I found the problem: I was executing a long-running 'cp' command at the time. This entry in kern.log was a brief clue:
Feb 21 08:33:59 jollyroger kernel: [129103.952479] cp Once the cp command was completed, suspend and hibernate started working again. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/722922 Title: Thinkpad T410 will not suspend or hibernate (immediately wakes up after suspending or hibernating) if external monitor is attached -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
