Finding system lockup problems

[notzippy]

Hi

This past week my computer has crashed 3 times, completely locking up (even reisub would not reboot). The var/logs/messages did not have a seg fault listed in them. But I suspect it may have to do with VirtualBox, the reason why was today I tried to put my machine to sleep but it kept waking up. Finally I shut it down and that process got hung up, but sysreq "rei" woke up the shutdown sequence , after stating something about interrupting the virtual box module. Any ideas on how I can track this down further ?

Not sure if this is related but one other thing I have noticed is that file writes seem to be a bit slow on my btrfs partition. it is mounted using the following options defaults,autodefrag,compress=lzo

Thanks
Nz