Version: (using KDE 4.3.0) Installed from: Ubuntu Packages I have noticed that notifications are shown when Kaffeine in is fullscreen mode. So far it is only Kopete, but there may be others. I believe Kaffeine should be able to call something like a presentation mode supressing notications totally and/or displaying only a smaller variant of them, not so intruding.
I can confirm this with kopete notifications and playing wesnoth fullscreen. KDE 4.4.2. I think it also happened to me with xine fullscreen, but I'll have to double check that. Possibly related to bug 225116
*** This bug has been marked as a duplicate of bug 177940 ***