Copied application showing "prohibited" instead of app icon in Finder I copied "Dead Island" to HDD from DMG file and it showed a "prohibited" icon instead of the game icon (2nd row, icon in the middle). I had to kill/restart Finder to solve it, but would like to know what is the cause for this and how can I prevent it from happening again?
I have seen Finder sometimes getting stuck still showing the last unfinished state of a file.  This may be a refresh issue, especially when you say that restarting the Finder solves it.

Alternatively, you could try to just run the application by simply double-clicking it.  If the "prohibited" sign is valid, you will receive an error message stating the cause.

Otherwise, it will simply work, potentially update the icon at that stage already or at least once you either restart the Finder or the computer.