Comment 90 for bug 577916

There seem to be 3 different issue, though any of them can happen, at random times:

1) Sometimes, when you suspend or hibernate (or when the battery goes low and the system is set to automatically suspend or hibernate), INSTEAD of hibernating/suspending it just locks screen. In this case, you can go back to normal operation by inserting the password and clicking "unlock"; however, it will never hibernate nor suspend (and in case the battery was low, power will ultimately go off and you'll lose everything)

2) Some other times, the suspend or hibernation process is started, but it HANGS at some point. In this case, there is nothing you can do except force power off physically by holding the power button.

3) Independently from all this, detection of the low battery condition does not work properly. I have my laptop set to automatically hibernate when battery is low. A lot of times, it simply happens TOO LATE, so the power goes off physically before hibernation is complete, even when hibernation itself is working properly. Sometimes, power goes off even before the system TRIES to hibernate.
Note that:
- the system DOES detect low battery, I can see it in the battery tray icon which is empty and red, and because popups appear a lot of times to warn me that the system will hibernate soon.
- Windows on the same machine hibernates properly on low battery, so it is NOT an issue with the hardware detecting low power too late (i.e. having a too-low threshold), it is an issue with the operating system that doesn't take action soon enough.

In my case, I've found out that issues (1) and (2) seem to happen only when I am running VirtualBox (a virtual machine software) or _after_ having run it. This probably means that there is a bug in VirtualBox which is preventing the host operating system to hibernate/suspend - however, this does NOT mean that there's not a bug in Ubuntu. Hibernation, suspending and shut down MUST always be bullet-proof and must always succeed even in presence of a buggy or even malicious program; if a buggy program can prevent hibernation to complete properly, the operating system has a bug in itself.