Z60m Doesn't Standby when Idle on Battery

[mrtom]

I've got my Z60m's power options to standby after 5 minutes when running on battery. The system ignores this and stays on until it hits the critical battery level, at which point it hibernates. Any ideas?

I should note that when I actively tell it to suspend via the Fn or C-A-D route, it does so without complaint, so it's not that something is blocking it from suspending, but that it's either ignoring the power options or something is keeping it from being idle.