I've been having this problem with all Unity Player run games. I have had to play on different PC's just to get my money's worth on these kind of games. Just to mention the games: Heartstone, Plague Inc. Evolved (steam) and Kerbal Space program(steam). I spent quite a while conversing with Blizzard customer service reps and man the answers, "troubleshooting" and "solutions" were just, how do I say this, fruitless. Anyway all this config, driver update, memory leak people talk about makes me think that the people who came up with these pseudo-solutions clearly don't understand the underlying problem. Unity Player has serious stability issues on certain Windows OS and hardware combinations. The so called memory leaks are caused by mishandled memory allocation(and possibly garbage collection) and read/write process between Unity Player and the OS. SO IN SHORT don't worry people its not you(and your rig) it's mostly the developers of the game choosing Unity Player and not knowing why this is happening.