Good questions, apologies for the vagueness.
- Download app from 3rd party site, haven't confirmed if something from App Store has the same problem.
- Copy app to Applications folder
- Icon appears in the Dock with the plusing "I'm launching" sphere beneath it.
- That's where it just hangs there, and clicking the icon in the Dock causes it to disappear and the launch to abort
I don't have an anti-virus running in the background, but I do periodically run ClamXav (about once a week).
I've tried uninstalling with AppCleaner
I've tried uninstalling manually
I've copied and replaced
I've emptied Trash, Logged out, restarted, tried the Terminal to flip quarantine bit workaround, etc -- all multiple times with no change in behavior
The App I'm currently battling with
I innocently updated from the previous (working) version just this morning and realized this had happened with another app last week.
I now see where you were going with this. When I read the thread https://discussions.apple.com/thread/3826648?tstart=0 the last entry talks about The Unarchiver. It reads
If you are using The Unarchiver 3.0 to unzip the application, it will not work properly when you launch it. This is because of the sandboxing feature in 10.7.
I understood this to mean The Unarchiver would not work properly, NOT the expanded app.
I used the Apple supplied Archive Utility and the app now works properly.
Thank you for the clarification and the assistance!