Hi Angela: I just sold my Classe 301 for the very same reason. It's definately the protection circutry kicking in, but if it will not go away, you've (A) either blown a fuse (easy to see when you take the cover off and easy to replace), or (B) fried a circut in the output stage, which is what happend to me. I will say that Classe fixed my amp and sent it back to me in 5 days at no charge under warranty, even though I was not the original order. Call Classe, they give excellent customer service.
The 300 is a high current amp with a monsterous power supply, as you know by the weight. For that reason, if you so much as short it out just once it can fry the output stage. That said, I think the Classe is a touch too sensitive and needs better protection circuts to keep idiots like me from doing silly things to an otherwise great amp. Above all, make sure your speaker cables are tigthened down securely! Mine shorted after the Rel sub cable came loose. --Lorne