Cards with DDR2 should be supported as far as I know.
Can you try a couple of things:
1) Before running either XBMC or xine, please run the following command in the same shell:
That might produce some extra useful information for us.
2) For the xine case, I assume you're using the overlay presentation queue by default. Can you please test the blit-based presentation queue, by running the following command before xine, in the same shell: