Parallels version: 9.0.23140 Host: Mavericks Guest: Windows 8.1 I'm using my parallels VM and it keeps flicking back to the first desktop without any explicit cause on my behalf after a few minutes. This occurs while doing random things in the vm. I isolation tested a third desktop, did not see the behaviour. Went back to the vm, saw the behaviour.
I am experiencing the same problem. The Windows 7 VM in full screen mode gets switched back to MAC desktop frequently and randomly. I am running Mavericks and this problem started with the last upgrade to Parallels Build 9.0.23140 (Revision 935944; Friday, October 25, 2013) which I installed yesterday.
Thanks Dave for confirming this. A colleague of mine suggested that turning off the "Displays have separate Spaces" setting in Mission Control settings. Seems to have fixed it for now.