Search the forum for "cuda hack". You can either modify the cuda_supported_cards.txt file or delete it. Either way, it will allow you to enable hardware MPE with your card.
Sorry to be bothering you but i searched for the CUDA hack you mentioned but it wasn't very detailed? Do you know of a better example?
I've bought exactly the same iMac...I rang Adobe tech support and they talked me through it...all works perfectly now.
with at least 1Gig of video ram, use the nVidia Hack http://forums.adobe.com/thread/629557 - which is a simple entry in a "supported cards" file - and Mac http://www.vidmuze.com/how-to-enable-gpu-cuda-in-adobe-cs6-for-mac/
You mention last week that you had the same problem as me with your new iMac and graphics card with cs6.
I was just onto Adobe and they told me that they could not assist.
Can you tell me who you death with?
I am really keen to get this card running!