Hi. I'm experiencing sporadic crashes on my Mac. Three times now while browsing with Safari the whole machine has locked up. The screen locks up completely and I can't click on anything; everything is unresponsive. It's quite weird because I can move the mouse freely but everything else is unresponsive. CMD+ALT+ESC doesn't even work, the only thing I can do is hold down the power button to reboot the machine. The machine boots fast like normal to the login screen, but logging in takes much longer than normal (up to 10-20 seconds). I repaired disk permissions yesterday. EDIT: And the two previous crashes happened a couple of days ago. I'm on a 2015, 15" Pro. I never encountered the same issue on my 2010, 13" Air which also ran Yosemite. Anyone else experience something similar?