Weird mouse problem

In around 75% of the times I start ET, my mouse (MX518) isnt working as it should. I cant move left/right and up/down, although I can shoot (mouse1) and walk (mouse4). I checked my mouse sensitivity, its not equal to 0. But when I minimize ET or go to the menu in ET my mouse is working fine, its just not working when Im trying to play ET.
I already reinstalled ET and setpoint.
I did not change anything in my cfg lately but I installed vista, dont know if its possible that vista is the problem.

Thanks in advance....