I have a cinema 20" and the power adapter seems to be bad, I try it with a 90w adapter at home and it works good, same thing with a 120w I believe is the one for a cinema display 30" adapter, this was tested at an apple store, they didn't have a 65w adapter, so I took it to another store where they had a 65w adapter and it didn't work so they guy told me that the cinema was broken and the repair cost $299 but the display is good because I tested at home again with a 90w adapter and it is okay, so my question is, could it be that the monitor needs a more powerful adapter to function or maybe the 65w adapter that they tried wasn't working either?
+I never really thought about that. Heck, I’m running the very first Apple flat panel display on my 2009 MacPro using the ADC/DVI adaptor. It works great and it provides a nearly 7-foot reach! Oh well, I learn something new every day...+