Joe, the popup is pariahware elastic window reg problem. I have gotten the unencrypted classes from Christian and have rebuilt app removing the key requirement code per window. My customer will hopefully be able to test it tonight. It is possible there is some other problem. We turned off the restriction for app store apps only but still got the error.
Tim, If the customer is installing a new copy of your app over the old one, they should delete the original and then install / copy the new one. We’ve seen a similar situation with our apps (both Xojo and Obj-C based) under Mavericks where an odd missing dylib, xib file, or plugin occurred. Deleting the original copy solved the problem.
Just FYI, a user does not have to turn off GateKeeper entirely. If they double click your app, they will be stopped from launching it, but if they right click (or control click) and choose Open from the contextual menu, they will get a similar warning but with an option to proceed with the launch.
@Tim Turner - Yes, simply deleting and emptying the trash works. For automations, I have a preupdate script which is part of my installer package that checks that the app isn’t running and then moves the existing app to the user’s .Trashes folder.