#1 - Nov. 15, 2010, 6:44 a.m.
Did you do a full reset UI previously, Grimp?
It's entirely possible that there is some corruption - character specific.
If you had said it was multiple characters - in one specific spot, I'd suspect corruption in a game file tied to a specific location.
To do a full reset UI, you will want to save your addons in another spot if you wish to preserve them.
Then rename/delete or move your WTF, Cache and Interface folders while WoW is shutdown. Reboot your system.
Note, if you are running Vista make sure your permissions are set so it does not undo your changes.
More detailed instructions for different operating systems, including Macs are here.
http://us.blizzard.com/support/article.xml?articleId=18761&searchQuery=reset%20UI&pageNumber=1