Alright, I still haven't got a new mouse, but I've upgraded to SP2, and updated and run Ad-aware, getting rid of about 46 adware files I didnt think I had (due to lack of updating.) It seems some time ago I uninstalled Spybot from my computer, not entirely certain why.
I've also cleaned the ball and such of the mouse, and it's running a bit better.
There's only been one incident in the past few days of the mouse freezing. (few days being, since I cleaned it out and updated and all that.)
So, it's back at a tolerable level, but it's been fine before, only to start being an extreme bother a few days later on other occasions too.