What apps do you have open? In fact if you can think of it when it happens the full output of the command

ps aux

Might help. My brain is a bit fuzzy right now on the details but I seem to remember something in an early Matchbox server where under certain conditions it would enter a loop/wait state waiting for a return that would never happen (the code that did the check and return was removed but the wait state to pause the rest of the code wasn't). Perhaps something like this is the case here as well.