Use Win 7 setting to adjust Parallels energy scheme
Had the same issue. My Win 7 would freeze (that is not wake up without freezing) if it had been asleep for more that one hour or so. The issue started after I updated to the latest version of Parallels - Build 7.0.15104 (previous to this update all was fine and I had no issue with Win 7 waking up from sleep).
Found out that the sleep option from the Win 7 Start menu/button is not necessarily doing what you expect it to do -- that is: a sleep is not necessarily a sleep. This is because Parallels has particular settings which seem to override the action/meaning of the sleep option from the Win 7 Start menu/button.
Parallels installs its own energy management option/settings/scheme. You will find those options under your power settings under your system settings in Win 7. You will find that you can specify and decide how windows should act as a response to a click on the Win 7 Start - sleep button. The particular action is adjusted by selecting the advanced options link and adjusting the behaviour for closing the computer’s lid or pressing the sleep button/switch.
Now make sure that the options for closing the computer's lid or pressing the sleep switch only activates the sleep option and *not* the suspend option (sorry for not knowing the proper function name on Win 7 UK/US -- mine is in Swedish).
This did solved my issue. I did not have to change any hibernation/sleep options on the mac side.
Last edited: Jul 30, 2012