After having run Parallels 10 for a more then a day with a Windows 8.1 guest, I get this headache issue when I quit parallels I suspend windows 8.1 from the parallels menu (that works) I Quit windows 8.1 from the Parallels menu (that works) I Quit Parallels 10, Suddenly I am logged off Then I need to logon again and all my previous opened apps restart, including Parallels that keeps starting up forever. Force Quit on Parallels works. Sometimes I can restart parallels and it works. Sometimes I need to completely reboot my Mac. I even had to reinstall parallels once. Does anyone recognize this behavior? It always happens when I quit parallels. I am using Yosemite, so it might be a 10.10 issue, but the fact that Parallels triggers this issue makes me ask around first.