BIOS update did not do the trick. HP Support Assistant finds nothing - all drivers up to date. Please note: the machine does not shut down unless the power plug is pulled and the battery is removed. (i.e. ctrl-alt-del does not work, the power button does not work). No apparent issues with dust/lint. Please advise re next steps.
Product Number: XG881UA#ABC
Windows 7 Home Premium 64-bit Service Pack 1 (updates on auto)
General occurrence, no pattern. Has been going on for a while now.