It happened to me yesterday in game. Skype bumped me out when a friend messaged me, and when I alt-tabbed back in my cursor had disappeared.
Except it wasn't compeltely gone, it looked like a VERY hard to see thing like this:
very faint lines, very small, maybe half an inch long on a 1366x768 screen with a 15inch diagonal.
It usually occurs when I quit starcraft, never had it happen in a league game before.
running an HD5470 on a Sony Vaio- and am therefore unable to update my graphics drivers ><