Yesterday I installed Ubuntu 11.04 from scratch on my Thinkpad R500, leaving the default power management settings.
Yesterday I closed the lid, and this morning when I opened it the laptop resumed correctly.
Today during lunch the laptop went to sleep without me closing the lid, and there was no way to wake it up by typing ESC or moving the mouse or TrackPoint. No disk activity at all. When I briefly pushed the POWER button, the laptop rebooted completely, losing my opened applications.
Is it a known problem with Natty/Lenovo Thinkpad R500/ATI?
Any idea what could fix the problem?