I was going to do a practice game in customs alone in Summoner's Rift, before beginning a PvP game and found myself unable to do so. The moment the load screen popped up the game would bug splat. I've tried it several times now with different champions, different amounts of bots all ending the exact same result.
I'm afraid to try a match in PvP with the game client doing this. I don't want to enter a PvP match and simply bug splat out of it and never even be able to touch the game.
I've played Twisted Treeline in customs and it is working fine for now. It may just be SR.