Macintosh

so i have to play on a mac now that my alienware broke (R.I.P.) and i installed the game and played it and the first launch went well and all, i played for about half an hour... then i logged out to switch characters and when i tried to launch it... my whole macbook pro crashed... i have tried launching it maybe 20 times and the result is the same every time. When i press play it opens up the game client and then just stays at a blackscreen and then a black square pops up saying you need to hold down the power button to shut down ur computer due to an error... i tried reinstalling and the same thing happens.

please help. my sub is just wasting away.