DVI to HDMI adapter not working


I plugged my PC into my HDTV (Sony Bravia) using an RGB cable (from a DVI output on my PC, and a DVI to VGA RGB Cable adapter). Picture looks great. Full 1920x1080 resolution. But, the audio RCA input is broken for that channel. So, to get audio from my PC to the TV i need to have the video come into an HDMI input w/ the audio coming into a corresponding RCA input.

I bought a Rockfish DVI and HDMI adapter and plugged that into the TV, and then the DVI cable into the PC. The TV doesn't recognize that anything is plugged into the HDMI slot.
I've tried moving the cable various other connections w/ no improvement.
I've tried restarting the PC w/ the DVI to HDMI cable in as the only video and still no improvement. The VGA cable works constantly and can be hot swapped in.
I'm confused on why this won't display through the HDMI port
could the DVI to HDMI adapter be broken? I only bought it today.

My computer is:
AMD: Athlon 64 X2 5200+ 2991 MHz
Mobo: Gigabyte M57SLI-S4 v.2
RAM: 4GB Mushkin DDR2 PC2-6400
OS: Vista 64bit SP2
VC: EVGA 8800 GTS 320MB


The TV had 4 HDMI ports...
i can label them so you can remember what they look like in the menu (which looks like the XMB interface of the PS3), which i've done
The ports are set to 'always' on. I've used the port for other devices before, so i know the physical port isn't an issue