Woo, update after a bit of searching.

It seems that back in November there were some issues with using 5770 card on 10.6.4. Do we know if these have been fixed by 10.6.7?

As far as I can tell from the older posts, there is no advantage to running in 64bit, and I can reset the machine to 32-bit. Is there still an issue with the card in 32-bit?