i had some similar issues. as soon as i added a 12th emulator to the startscreen(by placing a rom inside the folder) emulationstation frooze on startup. try to remove one system and it should work again. WHy this happens though is beond me (i myself removed my atari2600 roms to make place for n64 roms)
keep me updated when you find a way around this (i couldt find one. it happend for me with both pi 1b and now Pi 2, so the only answer i get : “not enough memory” cant be the problem (imo))
I had a similar issue a few weeks ago. Strangley, it occurred on one TV and not my other. The TV I has issues with is 1080p whereas the one that worked is 720p. I forced the PI to 720p and the problem hasn’t occurred again.
Btw, have you tried updating to the latest version of ES? I suspect it may help with this issue due to needing less vram.
^^ my other hobby