Computer is set to suspend after 20 minutes of inactivity, but it fails to do so. I have no idea how to debug this or even how to look for a fix (I searched a few strings, to no avail).
If anyone can give me a clue I would be quite grateful.
I'm using ArchLinux.

If you instruct your system to suspend manually, does this occur?
Also, does the system correctly turn the screen off, or take other actions it is supposed to when inactivity occurs?