I have a mid-2011 2.5 GHz Mac mini with the Radeon 6630M graphics, which last year I upgraded the HD to a Crucial m4 SSD and 8 GB of RAM. Running Yosemite 10.10.3. The other day I was watching a YouTube video and the machine just suddenly restarted without error or warning. Then after it came back on, 10 minutes later it did the same thing. Now it turns on, displays thick vertical purple or green stripes, shows the OS X boot up screen for a few seconds, then just goes blank (but the machine remains running). When it first rebooted without warning, I felt the machine and it was very hot. Could it have overheated and permanently ruined the graphics card/logic board? Is this a known issue? Since it's not under warranty anymore I assume Apple will do nothing?