I've seen this before with my amps; they go into shutdown to protect themselves. When the temperature falls slightly, they'll play again.

If the empeg timecode is still counting upwards, then the problem is most likely to be your amp and not the empeg. If the empeg stutters (and the elapsed time clock doesn't keep ticking) or fails to respond to button presses (etc) then there may be a problem with the empeg - or a bug in the player.

Hugo