Hi there.
Don't know for sure if it'll fix your problem but it certainly had resolved all the mouse issues I encountered with SP 3 so you might consider downloading and giving a shot at this great utility :
http://tinyurl.com/n6yffw
It's called MouseCTL.com and you have to copy it in your SP dir then add these lines to the .BAT file used to load SPWaW :
- loadhigh c:\local\dos\mousectl 5,6,10,15,15,15,15,15
It controls the speed and accelerations of the mouse cursor so you can try and experiment different variations.
P.S : the TinyURL is a convenient way to share some lengthy URL but if you prefer, I can e-mail you the file (only 3Ko). Maybe it's still possible to find the genuine one on-line but you'll have to search for it as I'm unable to remember where I originally found it [8|]