Weird mouse sens

I’ve recently installed IW2 again but I notice something strange, the mouse X-axis has a faster accel. to the right than to the left and the Y-axis has a faster accel. downward than upward :/
I don’t know what it is, last time the game was running on my system it didn’t have the problem. My system has changed a bit tho between the last time I played IW2 and nowadays.

Changes since the last time playing the game:
Windows XP SP2 (Last time running IW2 it was plain XP w/o SP2)
Newer drivers for vid card, audio chipset, VIA 4in1 pack.
Last but not least: I’ve got myself a shiny mx510 instead of the old logitech mouse I used to use

Arrogance is the pathway to competition