Want to borrow my cat?
Seriously, I've had this problem intermittently but not as badly as you descibe and not at the moment.
I believe it is not the mouse but Internet Explorer. If you are using 6.0 try going back to 5.5.
Try just reinstalling IE and reinstalling the security patches from the MS download centre.
If your mouse behaves properly with applications such as Word, Excel - or even just Windows Explorer - then it's probably OK.
What version of OS and IE are you on?