Forum:PS3 Seems to quit to XMB

First of all, its my first time posting here. So my text might not be formatted properly. If so I apoligze. Anyhow whenever i'm fighting a enemy seems to be random. I thought it was when i fought nightstalkers but now i've seen it do it with others it seems to just crash the game back to the XMB. Not the system where it needs a restart but just the game. Goes back to the XMB like nothing ever happened.