This looks like something I can reliably reproduce ATM on 11.10. If I close the laptop lid on my Lenovo T500 while on AC power, it suspends very quickly. If I close the lid while on battery power, the sleep indicator starts blinking. At this point, the machine starts to get very hot (the fan seems to stop running).
The sleep indicator stays blinking, and the power button does not wake up the machine. I have to hold power to power off completely, and then restart.
I haven't tested pm-suspend directly (vs closing the laptop screen). I'll try that next (just want to finish submitting this before I crash my machine again.)