This is something that I had encountered when testing VM’s in our PoC for XenDesktop recently. We could come back after a few hours and find the VM in a hung state or in sleep mode. The sleep mode symptom was a obvious sign of were to start looking. After playing with the power settings a few times and turning off all of the options the issues went away.
According to a new KB article from VMware this is more of a common problem. Stop by here for the original document.
