Are you using a wheelmouse I had a similar problem with a wheelmouse and I fixed it by using the cheatcode at boot "knoppix nowheelmouse" when I switch back to the knoppix machine it takes a few seconds to become active but after that it is fine.

This may or may not work as different hardware have slight variations on standards so you may need to try a different brand/model mouse and see if that fixes the problem.

Regards
Pete