Comment 8 for bug 94855

This is quite likely an ACPI problem. One of my questions was if you have ever been able to hibernate or suspend.

The HP website indicates there is a BIOS update for this motherboard:

http://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?softwareitem=pv-22976-2&lc=en&cc=us&dlc=en&tool=softwareCategory&product=428235&query=pavillion%20a650e&os=228

Another option to try is to boot with 'acpi=off' and try a shutdown.