[CLIENT] randomly goes to black screen

This has randomly occurred to multiple friends of mine. I was just playing a few games, which in fact worked smoothly up until my third match. I got into queue, and then entered champ select for like 2 seconds before all of a sudden the screen just went black and gave me an error message. Worst thing is, when this happens you have to log off in order for it to stop doing that. Otherwise, it will just occur again. It also counts against you for dodging queue, so you get banned for 5 minutes or more (based on your previous dodges). It would be a lot easier if this didnt count against you and even fixed >_<