Ok this is a pretty strange problem:
For quite a long time (probably since 11.10 upgrade) I didn't have any ubuntu related sounds (eg. Login sound quit window sound) It didn't bother me much and so i didnt post it on the forums.
But today while running strangely and I tried to kill it but accidently killed unity.
Because i didnt have a ui and the shutdown button on my pc didnt work i pressed the power button on my pc.
because i was afraid of corruptions in the system i immediatly rebooted.
Exactly the opposite i thought happened: the ubuntu sounds returned and everything else looked fine exept for one thing:
I still had the old wallpaper while in the change wallpaper menu my custom wallpaper was selected

What should i do to fix this
And a less important question: what happened to my system when turning the power off? Did some kind of memory get reset?