ista enters startup after hibernation

After Vista has been in hibernation for a while with the usual black
screen and I move the mouse or press any key, rather than wake up and
logon, I find the computer has fully shutdown and goes thru startup
without having to push the start button on the front of the tower.

It has only just started happening and I do not even know where to
start to stop this from occuring.

Any help would be appreciated.

Thanks in advance.


--
oah

Just to clarify, the system does a reboot when I move the mouse or hit
any key after being asleep / in hibernation rather than go to the logon
screen.


--
oah