Ah, i guess the problem comes from the card having both a radeon pci id and a second function which is listed as 1002:5d44, which displays as ATI Technologies Inc RV280 [Radeon 9200 SE] (Secondary) in lspci output, and it is this one that X is matching, not the primary one X knows about.
Adding BusID PCI:1:8:0 doesn't seem to help here. Friendly, Sven Luther