Escape doesn't always work to quit the emulation. But on every game I have, I can start the emulation and immediately hit Escape and it quits. It's only after some time playing that it does this. Perhaps after some other inputs. But I can't seem to duplicate the behavior, though I have been trying.
I've been playing Williams Pinball, in this I can make it happen there every time. Also, I have a dual monitor setup, maybe this is a key factor.
I load the emulation (fullscreen, primary monitor) hit ESC - it quits.
I load the emulation, play a game, then escape no longer functions.
I click once on the secondary monitor, then back to the primary and ESC functions again (almost like it's a focus issue).
If I disable the secondary monitor, same thing, I just lose the ability to click on the secondary and re-click on the primary, forcing an ALT-F4 to end.
Seems like all this is happening after a save possibly.
Well, maybe someone will see this and find it useful, but then again, maybe not
thought I'd put it all down just in case. Who knows, maybe it's well known and I'm doing something wrong 
I've been playing Williams Pinball, in this I can make it happen there every time. Also, I have a dual monitor setup, maybe this is a key factor.
I load the emulation (fullscreen, primary monitor) hit ESC - it quits.
I load the emulation, play a game, then escape no longer functions.
I click once on the secondary monitor, then back to the primary and ESC functions again (almost like it's a focus issue).
If I disable the secondary monitor, same thing, I just lose the ability to click on the secondary and re-click on the primary, forcing an ALT-F4 to end.
Seems like all this is happening after a save possibly.
Well, maybe someone will see this and find it useful, but then again, maybe not
thought I'd put it all down just in case. Who knows, maybe it's well known and I'm doing something wrong
ok, thanks for letting me know