Parallels Dekstop - upgrade from version 3 to 4 never finishes

If you have upgraded Parallels Dekstop from version 3 to 4, there is a mandatory upgrade f your virtual machines.

If your VM is Windows XP and you have Zone Alarm installed, it will never finish.

You need to click the 'lock' icon to go into manual mode, make your Zone Alarm selections, and the upgrade will finish.