Yes I am logged in as an Admin user.
I'd suggest trying to reset your preferences to see it that helps. You can just rename the preferences file or move it to a different folder. A default one will be created.
On the Mac, your preferences file is called "com.camerabits.PhotoMechanic.plist" and can be found at (starting with your home folder)/Library/Preferences/
Like I said, you can either move it somewhere like your Desktop, or you can rename it slightly.
Then try starting PM again. If that doesn't work, then if you want to contact me privately and give me your phone number, I'd be happy to assist you over the phone.
HTH,
-Kirk