I have a mid 2007 imac with a fresh HD (2 or 3 months old) and I upgraded to Mountain Lion several days ago.
Here is what has happened since:
1) Screen started dropping out (Going Black) but computer seems to be running in the back ground.
2) I read multiple posts...
a. Tried resets (w/ apple care on phone)
b. Disk Repair (w/ apple care on phone)
c. Fresh install of Mountain Lion (w/ apple care on the phone)
d. Tried to download Smart sleep, Fan Control, apps nothing would allow me to use with the opperating system.
3) I gave up, so I tried to use my Time Capsule to revert back to prior version of Lion ( 7/24/12 last back up)
after many hours going into the last bit the screen went back and I had to reboot, then this corrupted my time capsule and gave me an error message. At this point I have so many hours involved I am about ready to 😢.
4) This morning I gave up and put in my Snow Leopard CD and started from fresh.
5) Tonight I was able to access my Time Capsule, thank God but not through the normal back up process with Time Machine. I started to copy over the files to my HD and everything was working and then :::::: BLACK OUT AGAIN :::: this is with SNOW LEOPARD running.
So my questions is now was it really Mountain Lion ? or did Mountain Lion fry my graphics card? I am at a loss, I am so ready to upgrade to a new computer but still waiting on newest release. Oh well time to set up an appointment with a Genius.. I feel everyones pain who maybe experiencing these same issues.
Best of Luck