Comment 4 for bug 61405

I tied both hibernate and sleep actions, but using sudo as a user and from console as root. The result is the same in both cases:

Hibernate:

Successfully saves memory content to the swap partition and powers down. Then, out of the blue, about 2 minutes after that, it powers up. From the noise it makes, I'd say it reboots up to GDM, except that when it powers up, it returns to a pitch black display. Pressing any key or moving the mouse doesn't help. The only way to get something on the display again is to forcefully power off by holding the power button long enough for the hardware to notice and then power up manually to restart the system.

Sleep:

Starts saving memory to swap and then hangs with the drive LED remaining on. Left to its own devices and coming back 5 minutes later to check, it remained there. Again, the only way to get something out of the computer is to forcefully power off and reboot as described above.

One detail I forgot to add previously:

Hibernate and sleep previously worked fine with the Ubuntu 2.6.17 kernel.

A month ago, I had upgraded just Required packages and the kernel to Edgy, all while keeping the rest to Dapper (using APT preferences to pin * to Dapper), to be able to benefit from certain new kernel drivers added since 2.6.15. It only stopped working after I removed Dapper APT sources to completely upgrade to Edgy. This pulled in newer acpid, apci-utils and other software to manipulate ACPI from the GNOME logout panel.