My heart just stopped for 10 seconds (not literally)

[ibookowner2]

I come back to my Imac G5 rev B and awake it from sleep and all I see is a grey screen, my mouth drops and I sit in shock hoping that the screen will return to its old self, finally after 10 seconds my desktop appears and all is normal. Does anyone have any ideas what that is or could be.

Thanks

 

[Nermal]

My Intel did that yesterday, but I think I know why. I put the system to sleep the night before, then accidentally clicked the mouse. I then pressed Cmd-Opt-Eject (shortcut for sleep) before it had fully finished resuming. When I tried to wake it up then next day, I got the grey screen. It too fixed itself.