Damaged and can't be open app error message

In Terminal, run "xattr -rc /Volumes/Application.app", that should fix it (naturally, replace "/Volumes/Application.app" with your actual application path. No need to disable GateKeeper.

I have received the same "[Application] is damaged and can’t be opened." error when trying to run unsigned applications in Mountain Lion. Notably Davmail.

Try the "Allow applications downloaded from: Anywhere" setting in the "Security & Privacy" System Preferences pane :

For whatever reason you may be running an old, unsigned version of the app.

For a similar problem, with the (Java) application Sawmill, it was sufficient to "Allow applications downloaded from: Anywhere." I got the "damaged" error when I tried to run it; then I changed that setting to Anywhere; and now I don't get that error anymore. Looks like a bug in Mountain Lion, sort of: the error message could be a lot better, e.g., something saying that Security & Privacy settings disallow that application. Anyway, thanks for the suggestions; it worked.

From their FAQ:

iBoostUp fails to launch after an update with error "iBoostUp is damaged and can't be opened" We've had intermittent reports of this occurring with our 3.1 and 3.2 updates. This issue is not specific to iBoostUp and related to a problem with the App Store itself. To resolve, please: Remove iBoostUp from your Applications Remove com.ituneup.ituneup.plist and com.ituneup.ituneup.plist.lockfile from ~/Library/Preferences Download iBoostUp from the Mac App Store

In case you are unable to locate the above-mentioned files please try the following: Open Terminal.app from Applications -> Utilities Type "rm ~/Library/Preferences/com.ituneup.*" without quotes and then hit [enter] Re-download iBoostUp again from the app store.

To re-enable any of your previous purchases please follow the steps in FAQ entry #12