sorry for the last anonymous post.
the question for the restart is not considering my acutal prob. (it did not help anyway.) i'm new to *nix-systems and used to restart the system every time i did something special on it (from windows). so the question is more general: when do i have to restart my system? never?
This is extremely off topic, but ok... You rarely need to reboot your *nix machine. Only in case of a kernel panic, a kernel update, or when you want to add new (non hot swapable) hardware.
Update: ... or in case of really annoying zombie processes.