With the LiteHTML plugin loaded, the Reply/All/etc buttons in the message view window can disappear until they get redrawn. The easiest way to see it is: - Open a message in a new window - Scroll down (the scroll position does seem to matter; every position except scrolled to the absolute top appears to reproduce the issue 100%) - Open File > Page setup... - Hit cancel The buttons will disappear until you: - move the mouse cursor over them individually - resize the window vertically - shrink the window horizontally (making the window wider doesn't seem to redraw the buttons) The issue can also be seen less reliably with various combinations of resizing and scrolling the message view window.
*** Bug 4500 has been marked as a duplicate of this bug. ***