It displays fine here - no crash, no problems.
Are you using one of the HTML rendering plugins to display the html? If so, which one? I've viewed it with the Fancy plugin.

And regarding the UTF-8 Subject. To the best of my knowledge the Subject should state it's encoding, if it doesn't it's broken.

Obviously I'm trying to do many things at once... Following up to my question about an HTML plugin, I now see that you are using the Gtkhtml2 Viewer plugin.

  Thank You, Paul. The bug really locates in gtkhtml2 plugin. But "fancy" complains me to the undefined symbol and, so, doesn't load:
=========================================================
fancy.so:
/usr/lib64/claws-mail/plugins/fancy.so: undefined symbol: webkit_web_view_get_selected_text
=========================================================
  Of course it may be compilation bug in my OpenSuSe repo.

  And WRT subjects, the non-mime encodings is a bug of about a half of internet (php, AFAIK) mailers in non-ASCII sector, because most of them are written by english-spoken programmers. So, stupid php-coders have no idea on how to adopt some out-of-box mail() function :(

The 'undefined symbol" in Fancy has been reported (many times) and fixed, see bug #2507. I don't think you have to necessarily be English-speaking to be a "stupid" php coder.

In the case of the attached msg, the subject is not UTF-8 but cp1251.

Created attachment 1052 [details]
New, but buggy fancy plugin.

  Hi Paul, I recently compilled&installed Fancy 0.9.14 from http://www.claws-mail.org/plugins.php, but the bug is still here.
fancy.so:
/usr/lib64/claws-mail/plugins/fancy.so: undefined symbol: webkit_web_view_get_selected_text

 Moreover, mailer now crashes when trying to load it again:
============================================================================
Claws Mail version 3.7.10
GTK+ version 2.24.7 / GLib 2.30.1
Locale: ru_RU.UTF-8 (charset: UTF-8)
Features: IPv6 iconv compface GnuTLS LDAP JPilot GNU/aspell libetpan libSM
Operating system: Linux 3.1.0-1.2-desktop (x86_64)
C Library: GNU libc 2.14.1
--
[Thread debugging using libthread_db enabled]
[New Thread 0x7fb1e4215700 (LWP 27598)]
[New Thread 0x7fb1f1621700 (LWP 27593)]
0x00007fb1fd1c58bd in waitpid () from /lib64/libpthread.so.0
#0  0x00007fb1fd1c58bd in waitpid () from /lib64/libpthread.so.0
No symbol table info available.
#1  0x000000000049f18b in ?? ()
No symbol table info available.
#2  <signal handler called>
No symbol table info available.
#3  0x000000000000438e in ?? ()
No symbol table info available.
#4  0x00007fb1e280fdea in plugin_init (error=<optimized out>) at fancy_viewer.c:1132
        directory = <optimized out>
#5  0x00000000005e982d in plugin_load ()
No symbol table info available.
#6  0x0000000000634666 in ?? ()
No symbol table info available.
#7  0x00007fb1fc71ea14 in g_closure_invoke () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#8  0x00007fb1fc73099a in ?? () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#9  0x00007fb1fc73a021 in g_signal_emit_valist () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#10 0x00007fb1fc73a1c2 in g_signal_emit () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#11 0x00007fb1febd1c95 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#12 0x00007fb1fc71ea14 in g_closure_invoke () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#13 0x00007fb1fc73018a in ?? () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#14 0x00007fb1fc73a021 in g_signal_emit_valist () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#15 0x00007fb1fc73a1c2 in g_signal_emit () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#16 0x00007fb1febd0abd in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#17 0x00007fb1fec7a958 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#18 0x00007fb1fc71ea14 in g_closure_invoke () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#19 0x00007fb1fc7307cf in ?? () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#20 0x00007fb1fc739df3 in g_signal_emit_valist () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#21 0x00007fb1fc73a1c2 in g_signal_emit () from /usr/lib64/libgobject-2.0.so.0
No symbol table info available.
#22 0x00007fb1fed93911 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#23 0x00007fb1fec78b13 in gtk_propagate_event () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#24 0x00007fb1fec78e73 in gtk_main_do_event () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#25 0x00007fb1fe8e464c in ?? () from /usr/lib64/libgdk-x11-2.0.so.0
No symbol table info available.
#26 0x00007fb1fc25958d in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#27 0x00007fb1fc259d88 in ?? () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#28 0x00007fb1fc25a2c2 in g_main_loop_run () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#29 0x00007fb1fec77ec7 in gtk_main () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#30 0x000000000044cfc9 in main ()
No symbol table info available.
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
============================================================================

file /usr/lib64/claws-mail/plugins/fancy.so
/usr/lib64/claws-mail/plugins/fancy.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=0x8afc87fb166759f7c415d77b9058f827325b1739, not stripped

  Unfortunally, I don't know how to see .so version, but in strings I cat find "0.9.14", so I think it's really new one.

"In the case of the attached msg, the subject is not UTF-8 but cp1251."
  Of course, in this specific case it is. But in more wide case, for example, all mail from ru-ncc@nic.ru robot (.RU top domain registrar) comes with plain KOI8-R and without any MIME. And I just can't see mail source because all 8-bit symbols are replaced with "_".

  The example of non-readable UTF-8 MIME:
To: =?UTF-8?Q?=D0=94=D0=BC=D0=B8=D1=82=D1=80=D0=B8=D0=B9=20?=<ds@miran.ru>
From: =?UTF-8?Q?=D0=A1=D0=B8=D1=81=D1=82=D0=B5=D0=BC=D0=B0=20=D0=B1=D0?= =?UTF-8?Q?=B8=D0=BB=D0=BB=D0=B8=D0=BD=D0=B3=D0=B0=20?=<billing@miran.ru>
Subject: =?UTF-8?Q?=D0=98=D1=81=D1=85=D0=BE=D0=B4=D1=8F=D1=89=D0=B8=D0=B5?= =?UTF-8?Q?=20=D0=B7=D0=B2=D0=BE=D0=BD=D0=BA=D0=B8=20=D0=B7=D0=B0?= =?UTF-8?Q?=20=D0=BC=D0=B5=D1=81=D1=8F=D1=86?=

  Encoded by MIME::Words in one of my perl scripts, but I see "_" in place of russian characters, while in RoundCube I see correct strings.

About the "undefined symbol" problem, use the CVS version of Fancy :
<http://www.claws-mail.org/snapshots/plugins/>.

"use the CVS version of Fancy"
  Great, it works! :)

  Now, another irregular crash orrures while I navigate through the preview list (generally, crashes just on plain-text mails). The up-to-date OpenSuse 12.1 is still on my PC (oh,no! the fixed kernel is at last released).

Claws Mail version 3.7.10
GTK+ version 2.24.7 / GLib 2.30.1
Locale: ru_RU.UTF-8 (charset: UTF-8)
Features: IPv6 iconv compface GnuTLS LDAP JPilot GNU/aspell libetpan libSM
Operating system: Linux 3.1.0-1.2-desktop (x86_64)
C Library: GNU libc 2.14.1
--
[Thread debugging using libthread_db enabled]
[New Thread 0x7ff938f91700 (LWP 6308)]
[New Thread 0x7ff939792700 (LWP 6307)]
[New Thread 0x7ff9421ab700 (LWP 1733)]
0x00007ff954a9c8bd in waitpid () from /lib64/libpthread.so.0
#0  0x00007ff954a9c8bd in waitpid () from /lib64/libpthread.so.0
No symbol table info available.
#1  0x000000000049f18b in ?? ()
No symbol table info available.
#2  <signal handler called>
No symbol table info available.
#3  0x000000000060c5bd in gtk_cmctree_node_get_row_data ()
No symbol table info available.
#4  0x0000000000598597 in ?? ()
No symbol table info available.
#5  0x00000000005a1127 in ?? ()
No symbol table info available.
#6  0x00000000005a1323 in ?? ()
No symbol table info available.
#7  0x00007ff953b31d6b in ?? () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#8  0x00007ff953b3058d in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#9  0x00007ff953b30d88 in ?? () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#10 0x00007ff953b312c2 in g_main_loop_run () from /usr/lib64/libglib-2.0.so.0
No symbol table info available.
#11 0x00007ff95654eec7 in gtk_main () from /usr/lib64/libgtk-x11-2.0.so.0
No symbol table info available.
#12 0x000000000044cfc9 in main ()
No symbol table info available.

The mail where Claws has been crashed this time was (plain-ASCII):
==========================================
Return-path: <nob.apc@miran.ru>
Received: from [91.142.80.6] (helo=sm1.miran.ru)
	by post.miran.ru with esmtps (envelope-from <nob.apc@miran.ru>)
	id 1Rs3DP-00083k-GJ
	for adm@miran.ru; Tue, 31 Jan 2012 06:12:59 +0400
Received: from bill.miran.ru ([91.142.80.22] helo=nob.apc.miran.ru)
	by sm1.miran.ru with smtp (envelope-from <nob.apc@miran.ru>)
	id 1Rs3DO-0003WL-UK
	for adm@miran.ru; Tue, 31 Jan 2012 06:12:59 +0400
MIME-Version: 1.0
Date: Tue, 31 Jan 2012 02:12:52 GMT
To: adm@miran.ru
From: nob.apc@miran.ru
Cc: 
Subject: UPS: Started a self-test.
X-Mailer: Email Server
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 7bit
X-Antivirus-CLAM: passed 
Message-ID: <1Rs3DP-00083k-GJ@post.miran.ru>

Name     : Smart-UPS 2200
Location : NOBEL
Contact  : MIRAN
http://nob.apc.miran.ru
http://172.20.0.16

Serial #: BA0902029648
Device Ser #: JS0520005128
Date: 01/31/2012
Time: 05:12:48
Code: 0x0137

Informational - UPS: Started a self-test.
==========================================