Cannot turn in quests in Outland

Have you tried a full reset UI, Danomi?

I'd definitely give that one a try first, and before you add back ANY addons.

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