David, good news!
Looks like there is a fix to our "LED Cinema Display (24-inch, Late 2008): Intermittent flicker while connected to a Thunderbolt port" problem.
Update your Cinema LED Displays Firmware according to this KB: http://support.apple.com/kb/TS4045?viewlocale=en_US
This is how it looked with my display:
I will report back if the fix works.
Experiencing he exact same issue. My monitor goes black, and the OS can't seem to read that it's a monitor ive connected.
No display is avaiable, however the on/off button on the monitor turns the macbook on/off.
I'm using Apple Cinema 24" with a MacBook Pro late 2011. I use a DVI to MiniDisplay adapter in between.
Often my monitor runs fine for hours, then suddenly its locked in black and stays that way even for days, then suddenly the image appears again and I can use the monitor for another set of hours, then it goes black again.
Rebooting doens't seem to affect the issue, and ive tried moving the monitor when the image appears to see if its a loose connection, however this does not seem to be the case. I've had this issue before ML, it startet back in Lion, but it's deffently being worse with the upgrade to ML.
Same thing happened to my 2-year old 24" Cinema Display. It would randomly blink out. Ran through all fixes; ended up the screen was fried because Apple monitors are not trustworthy. The Apple Store told me I would have to pay $800 to fix it because I didn't spend the extra $100 in AppleCare so they will stand behind their products. It was shameful. I'm just opting to never buy an Apple display again. I'm actually considering never buying from Apple again.