T400 running Windows 7 does not power off after shutdown

[jaws]

My T400 (276553G) (running Windows 7 Professional 32-bit) DOES NOT POWER OFF automatically after I shut down the machine. The same thing happens when I hibernate or enter standby; Windows does shutdown/standby/hibernate without any errors, but the notebook does not power off automatically. I have to unplug power and keep the power button pressed for about 5 seconds to power it off. BIOS, Think drivers and Windows are all up-to-date. I appreciate your help!