Mine went into protect once, and it wasn't thermal. Shoot, it's never gotten all that hot... and I've played it at full tilt for hours. It was caused by two ring terminals that I forgot to grind the burrs off of after drilling them out. They weren't seated well, at all. It was a stupid thing to overlook, and it caused a bad electrical connection. Have you checked ALL of your electrical connections to make sure they're good and tight? It could be just one bad connection. That's all it takes. And if you play it hard with bad electrical, it can damage any amp..... Which may also have been what happened. Bad things happen when you you're learning how to do something as you are doing it, rather than before hand. Been there. Multiple times.