I went out on my deck with my 13" rMBP to play music. It was sitting on a glass table, with full circulation available. It's 82 F and it was in direct sunlight. The top case got really hot and the computer stopped responding--couldn't click on anything, caps lock wouldn't respond. I was only out for about 5-10 mins. Brought it back inside and after two minutes everything was working normally with no restart needed. Called AppleCare and they recommended resetting SMC and PRAM. But this seems very specific to having been in the sun.