This morning, when launching an application I purchased from the App store some time ago, I was greeted with a sign-in box telling me that Apple needed to verify the application. I signed in using my iTunes password (which I've since double checked, and I know I entered accurately), and was greeted with the following message in reply:
Your device or computer could not be verified. Contact support for assistance.
Some poking about online shows one thread from a couple years ago where someone says he called Apple and they told him to delete "the plist", but that's all the information given. Deleting
~/Library/Preferences/com.apple.AppStore.plist did nothing to change the issue, however.
A couple of these applications are required for work. Any ideas on what the issue is or how to fix it?