New 27" Late 2012 iMac Screen Goes Black -- Am I missing something?

This is my second new 27" late 2012 iMac in the last 3 weeks. The screen on the first one went blank at random twice during the first 10 days (while I had just been using it so it wasn't a sleep issue).

I've had the replacement machine now for 1 week and tonight,I was waiting for dropbox to sync as I had uploaded a large file from my macbook pro.

I checked the iMac to see if the file had downloaded yet to the iMac, and as I pulled my hands off the magic trackpad, the screen went blank and I heard what sounded like the drive powering down - almost the sound of sleep mode when you close the macbook pro. I tapped the touchpad and the iMac was back on.

I've read about the two issues below, but I'm hoping that as a relatively new mac user, that I'm missing something obvious.

I love this machine and don't want to return another one.

1) that for others it happens when the screen is at full brightness (which mine is not)
2) it's a heat issue with the SSD.


Any advice is MUCH appreciated.
Thanks!

 

No and it's a good question, thanks. I even double checked the corners and it does the usual stuff - no quick sleep.