Generally speaking, Asil, when one's system messages cease to display, it's an indication of some conflict between one's standard User Interface (UI) and a third-party addon that has been installed. As such, you should be able to resolve the matter by following the steps below at your earliest convenience to restore your interface to its default settings:
Q u o t e:
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.
Let us know what effect, if any, that process has on the issue you're experiencing. There may be other avenues to pursue, but this is a good place to start. :)
Edit: Blast you Devilsaurs and that accursed stealth of yours! *shakes fist*
[ post edited by Pavonum ]
Ce sont ces fenêtres qui m'appellent...