Yesterday i've formated my PC and installed Windows 7 again. Everything is fine, however, some tray icons are missing, like Comodo Firewall and Realtek HD Audio tray icons. Could this be related to some Windows Updates or something?
I checked Task Manager and the program processes were running (Comodo/Realtek), just the tray icons were missing.
Hmm, it seems that since i've sweeped the registry with CCleaner, all of the tray icons are showing up now. Must have been something, but i don't know what it is...
Anyway, thanks for your help Herr_Koos, if the problem reapeares i'll post again.