I've recently updated to Ubuntu 14.04, and League of Legends and World of Warcraft have both stopped working.
With World of Warcraft, there are no error codes provided, and it just doesn't allow me to open the applications.
With League of Legends, the game client opens and allows me to log in, but once I'm in game, the shop you use to buy items freezes as soon as I click to open it.
I also found another problem. I closed my League of Legends game over an hour ago that was being played on PlayOnLinux. I then started to play Warthunder on STEAM, but that game froze in the queue finder, and League of Legends was there in the background, even though the game has been closed for over an hour.
I don't have any idea why it's doing that, and it could be many things maybe causing it.