Radeon x1650 in my Dragon 2 Platinum

I have recently received an HIS Radeon x1650 pro IceQ 512 video card (AGP 8x) for use in my Soyo Dragon 2 Platinum motherboard. I have the latest bios for the motherboard installed, and with the x1650 properly seated, the system does not post. Installing the x1650 in a different motherboard (newer model but different processor slot and no Dual Channel support), the video card works properly. Installing my old ATI 9800XT 256 in the Dragon 2 Platinum, the system works just fine.

I've read of some issues getting this card to work with the Dragon 2 Platinum since I've started looking, and I know at least some version of the x1650 should work on my motherboard. Is it the amount of video memory, something to do with the HIS version of the card, or am I just completely clueless (it's possible this alst one applies along with one of the others )? Any help would be appreciated.

Both power supplies are 500w. I even swapped out power supplies with no luck. The Dragon 2 Platinum motherboard is a discontinued product (like most of Soyo's MBs nowadays) so they don't provide any support for it beyond the downloads already available on their website.