Default email app keeps changing to parallels app

Mountain Lion, 10.8.1, Parallels 7, most recent update

Suddenly I find that my default email reader in Apple Mail preferences keeps changing to a Parallels Application (Windows Explorer (VMName)).

I change the default email reader back to Mail (6.0) but as soon as I close the preferences windows it changes itself back to Parallels apps again. And when I click on the drop down to select another app (Mail 6.0) I get a long list of every conceivable Parallels app.

Any suggestions/ideas would be welcome.

thanks