Hello FJJP...........
Are you using a surface with sufficient texture to allow the optical mouse to work properly?
Yes
Is there a device/software conflict?
No
Have you tried troubleshooting in device manager?
Yes
If you're using a USB hub, does it have its own independent power supply?
Direct into MB USB port
Does it work if the computers are completely disconnected?
This is the really weird bit.......no
Is the setup on one computer interfering with the other?
No
Have you tried a clean mouse driver install from the manufacturer's website?
No....but driver is the same and it would not affect the PS/2 mouse
Very odd..........especially as it is working perfectly now.......but will be dead when I power up tomorrow morning
Regards
FBW