Frustrating problem here - the shortcut to take a snapshot (Shift+F5) works fine. When I try to show the snapshot by pressing F5 (no modifiers) I see the screen blink very quickly, as though I'm very rapidly tapping the key, even though I'm holding it down. Has anyone else experienced this problem?
I'm on a 2012 Retina MacBook Pro, have the default system keys turned off in system preferences, and AE has "Use System Shortcut Keys" unchecked. Clearly it should be working since it briefly flashes. If I click the actual "Show Snapshot" button in the comp viewer it works fine and stays on as long as I hold it down. I'm running CS6 188.8.131.52
I would look at any macro or keyboard modifying applications on your system. I am running the same Retina MacBook Pro and the keyboard shortcut is working just fine.
Ah, yes, right you are. I was running BetterTouchTool, which seems to confuse it. After quiting and re-opening BetterTouchTool though, all seems to be working again.