Strange Behavior for Sleep Mode

[benchlegs]

Periodically when I put my 6.1 Macbook in sleep mode, the screen turns black, but the finder arrow stays on as does the apple on the cover.

In that mode I can't do anything and have to force reboot. Does anyone have a clue as to what could be causing this? And as I said earlier, it doesn't happen every time.

Thanks for any help.

 

[accessoriesguy]

does this always happen? have you turned it off and on, if its a rare occurrence, which sometimes people experience a simple restart sometimes sets it straight.