That doesn't sound normal, unless the chat tab filters were changed to not display any information. I recommend these steps:
1) Log out of World of Warcraft to your desktop, thereby exiting the game completely.
2) Navigate to the World of Warcraft folder, which is often found in the Program Files directory (the default path is C:\Program Files\World of Warcraft).
3) Either rename (or delete) the WTF, WDB, and Interface folders. (Note: If you do not wish to permanently lose any third-party addons you may have accrued, or macros you've written for your characters, you would be well-advised to merely rename the folders, rather than delete them entirely.)
4) Log back into the game by double-clicking WoW.exe, ensuring that you do not reinstall any addons before doing so.
I do not kill with my gun; I kill with my heart.