I have just installed a new mouse and has as a consequence expirenced some wierd instability with my sensetivity in ns... Once I enter the game, the sensetivity is fine. But after having played a while the sensetivity suddenly changes without reason... The sensetivity value in ns is still the same, but the actual sensetivity of the mouse has changed dramaticly...
Does anyone now how I can fix this problem?

What mouse and OS are you using?

I have a mx510 an i'm using windows xp

I have experienced this issue in the past. I posted about it in the Beta Bug Reports forum a while back: http://www.unknownworlds.com/forums/in...&hl=sensitivity
I haven't experienced this issue again since i posted.
Coincidentally, i have the same mouse as you.