I just reinstalled my computer and had to reinstall BF2 as well. But now all my controls are default again and I don't really remember which Sensitivity Settings were the right one.
So what settings are you using?
Mine are:
Infantry: 1.5
Land Vehicle: 1.0 (helps small adjustments with high zoom)
Helicopter: 3.0 + Invert
Jet: 3.0
Also, I switch my mouse between 800 / 1200 / 1600 dpi often too
Well, for land vehicle I think it depends on the map; In urban environments I find it a lot more useful to have a higher sensitivity (2 to 2.5 or so). When gunning for an APC at Mutrah, I need to be able to rapidly scan the environment because AT infantry could be lurking anywhere, and an enemy APC could come around the block behind us at any moment. I need to be ready to lay down fire in any direction, and thus higher sensitivity is better.
As for helicopters, I fly with a joystick. A pretty loose one. So I need to turn the sensitivity down because otherwise the smallest movements are way too much.