There is an entire article on the Wacom Cintiq customer care knowledgebase, which includes:
Are Cintiqs compatible with Mac using the MiniDisplay Port?
Yes, however, we have had a few reports of no signal, or, in some cases artifacts visible when using the Apple MiniDisplay Port to DVI adapters.
Many have reported success by using the Apple MiniDisplay Dual link adapter:
or the alternative Kanex MDPORTDVI MiniDisplay to DVI-I adapter with would connect directly to the Cintiq without having to use the DVI-I to DVI-D adapter that comes with the Cintiq.
You can find more information on Wacom's page:
hello, I know this is an old thread, but by chance did anyone figure this problem out? I have been around and around trying to get a used cintiq 21 ux to work with my macbook pro. it will work with a DVI to VGA adaptor, then VGA to mini port, but it will not work when using just a dvi to mini port as it should. it gives a "no sync, go to sleep" error message. I have trouble shot and trouble shot. wacom has suggested I ship it to them (on my dime since it's out of warranty) because they think it is the "main board". this will cost me hundreds, so I'm hoping it's an easier fix. I've heard of a lot of people having a hard time with their macbook pro's communicating with a wacom cintiq. I'd love any suggested solutions! (btw, I've tried 3 different DVI to mini port cables, it's not that, lol)