Could you please also try Option "BusType" "AGP" (or leave out that option) together with Option "DmaType" "PCI" ? This to see if it's just the DMA transfers that break.
Could you please also try Option "BusType" "AGP" (or leave out that option) together with Option "DmaType" "PCI" ? This to see if it's just the DMA transfers that break.