The audiohd driver for 2009.06 has a lot of problems, and you will find many posts about it. For many (not all), the problem is fixed by using the binary from the 2008.11 release. I don't know about your graphics card being misidentified.
For me, I replaced /kernel/drv/amd64/audiohd and rebooted. Fixed all my audio problems! -- This message posted from opensolaris.org
