The text in the currently selected line of the folderlist/summary/addressbook is white on bright blue/orange/whatever (depending on gtk-theme). Unselected items are fine, black/blue/bold (depending on state) on white/grey (alternating). Btw, the treeview in the preferences windows is fine, too - it keeps the foreground color at black.
I think the term "bright" is wrong, sorry. "light" or "pale" is correct. The contrast between foreground text and background is extremely low.
Eseentially, it's your GTK theme, but also in relation to how these various lists are built internally.
Well, it's the Ubuntu theme (Human) so a lot of people will be affected...