This might help, but I'm not sure it's your exact problem. Have you tried just booting your Mac with the Win7 DVD (hold down the Alt key after you power on)? If you do that and it asks you to 'Select CD ROM Boot type' then you need to re-burn your disc.Do you know the fix for this? On a side note, the release candidate dvd had no problem. Weird.
I tried that already and mac HD is the only available option.