sleep + hibernate problems on X61 tablet

[EPJ]

I've upgraded my X61 tablet to windows 8 pro. I haven't checked all the tablet functions yet but otherwise it seems ok except that I have a problem using both sleep and hibernate. If I try to use these I get a full reboot with an error. All the power options etc should be set correctly for hibernate to operate and it worked flawlessly under Vista.

I have checked event viewer > windows logs > system which shows a critical kernel power error, event id 41, task category 63.
"The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly."

This doesn't give me much useful information to go on. If anybody can point me in the right direction to solve this I would be grateful.
Thanks. Eric