I'm sure Bob could give you a long, wonderful explanation about why the server issues are happening, but here's my short and sweet non-technical reasoning. BlueHost has certain limits to activities sites can perform. This site routinely goes over that limit because of traffic. For a while BlueHost had given us a free pass, but it seems as though they've turned back on the restrictions that punish us for being popular.
All I can say is that we are moving to a new server soon and that should do away with the dreaded CPU screen forever. We can't promise there will never be another error, but we can hopefully count on it not happening several times a day causing my keyboard irreparable damage from my head slamming into it.