I just had this happen to me- it had gone into safety mode.
Lucky mine was in warrenty and they fixed it. They asked me if i had rewired it recently or changed seakers (i had done neither)..
This used to happen to mine when played at high volume. It turns out that the tweeter driver on my centre channel speaker was on its way out. I identified this by disconnecting each speaker in turn and seeing at what point the amp cut out.
Good luck,
Dave