X crash after exiting 3d game

[Faust Nijhuis]

Hello,

I' am running kubuntu 9.1 (updated) with nvidia (GeForce GT 220).

Every time running a 3d game (openarena, urbanterror) the sound will
go off after about minute.
And X will crash every time when I leave (pressing exit) the game.

I'am using the standard X config from nvidia-xconfig.

What can cause these problems?

Faust