Does Parallels prevent automatic sleep?

I'm beginning to have a suspicion that Parallels (3, latest update) installs something that prevents automatic sleep on the Mac, even when Parallels is not running. I know that it prevents automatic sleep while a VM is running and that makes sense. However, both my MacBook Pro and my Mac Pro will not sleep automatically, although nothing else seems to be wrong with them. Both have no problems sleeping manually -- they both go to sleep fine if I select Sleep in the Apple menu and the MacBook Pro will also go to sleep fine if I close the lid or if it is at the end of reserve power on battery. But neither of them will go to sleep automatically, even if there are no programs running at all, and the MacBook Pro will also never spin down the hard disk. I've gone through all the system settings again and again and there is nothing there that could be causing it -- I also temporarily turned off all synching activities, Mail, wake on modem, wake on LAN and anything else that might possibly be keeping the computer awake.

This is unlikely to be a coincidence on both computers. The only thing left, and the only common factor, is Parallels. Has anyone else noticed this?

 

If Parallels VM is not running, it cannot prevent Mac to go to sleep

 

That sounds logical but frankly I have my doubts. Parallels makes some quite far-reaching changes when it installs itself and I think it is quite likely that it does something to the OS X settings/mechanisms that also has an effect when Parallels is not running. I'm not saying that it's so, but it would be possible and AFAIK Parallels also messes with the Windows OS to enable Parallels to run a Boot Camp installation in a VM.

 

Parallels services are running only hypevizor and network interfaces, USB connect,
I believe if you check Console logs, you will found the reason