Comment 22 for bug 1176647

Regarding the backends, I used gl/x11 for the last few days and did not encounter the lockup. While at the same time, the machine will lockup instantly (after 5secs) when using -vo xv. Sorry, that this does not confirm your suspicion but maybe my gl backend does not trigger the code path you mentioned.
Maybe unrelated but I noticed my system was running very hot but the CPU was idle and powertop also said the CPU was running the lowest frequency mode (800 MHz), the system temperature almost reached 100 degrees celsius. After I rebooted the system now runs at about 40 degrees which I consider normal. Unfortunately the system is now unable to generate output via external display connector VGA1. I hope this is not a hardware damage and will try to generate output using a live CD and another computer. Also probably unrelated since 13.04 I experience suspend/resume bugs, where the system crashes on resume. All this issues together are very annoying and I am considering downgrading as well.