My PS3 hangs occassionally (several times a day).

It will hang:

1) sometimes when playing or loading a game (flying aces of WW2 or Call of Duty).
2) it will hang when I am at the PS3 menu and navigate to the Game loaded in the PS3 and select by pressing the X or selecting play from the menu for the PS3 game.
3) it will hang when I am done playing the game and want to exit the game and go back to the PS3 menu.

The only way to free up the unit is to completely powercycle the PS3.

I have download and loaded the latest patches.

Is this a bug? expected? a hardware issue? I have the 20gb model.

Please advise.

Thanks,
Sparkster