Cursor is erasing when it shouldn't
 

In my Maya 8, Windows7 the cursor occasionally leaves a trail of erased image wherever I move it. After a bit of clicking I can get rid of it and carry on working.
I've tried restarting Maya, working in a fresh scene, and rebooting my PC but the problem persists.
Any suggestions anyone?

Have you got a screen shot that might help.......dave

I've been doing some help swatting and I think my problem stems from doing naughty things while still in 3Dpaint tool.
Whose law is it that says 'When all else fails read the ****** instructions'?
Thanks for your interest, I'll do some more testing and come back if I find anything significant.