Although there might be another explanation, for this, I don't know enough about Parallels to know. I have a Windows executable set up as an app on a Mac desktop. It is a single-user database app that counts locked records in a database table to determine allowable users. When it is run, it now displays a message that is normally the result of another instance of the app running on the same computer, but the other instance cannot be "seen." When the Mac is rebooted, the problem persists. Is it possible that the Windows environment is going into some form of hibernation when the Mac is rebooted? That is the only explanation that might make sense. Thanks!