Go to the DEvice manager.
start - controlpanel - system - hardware tab - device manager
Go to the part that says, mice and other pointing devices then PS/2 mouse then choose uninstal.
After this restart your pc by pressing ALT and F4 for a couple of time until you see the log off box then with the arrow keys choose restart then press enter.
On restart the mouse driver will instal automatically again.
I'm guessing that on a restart previously, the mouse has been moved while the driver was loading and it may have thrown out the settings which could cause the hardware and software to not be in synch.