Now, I don't want this to sound arrogant, but is it a mouse with a roller underneath. You're showing classic signs of dirty conctacts. Take the large ball out and look inside for small rollers. There should be 2 ad 90 degrees to each other.
Another thought is a wireless mouse with a battery on the way out.
thirdly have you go more than one pointing device connected? These may be conflicting.
Hope thats not egg and possibly of some use,
CBA