If it's wired then you rule out the interference thing. You seem to have done everything I'd be able to suggest other than the last resort of a new mouse.

I know it's a pain and an unnecessary additional expense but could be worth a try. Even borrowing one would be worthwhile. I'm thinking along the lines of an irreconcilable software interaction between the game and the mouse system that may be resolved by using a new (probably brand name) mouse.

Good luck!