lopsided bandwidthTest: D->H is 3X slower than H->D

I recently purchased an eVGA non-overclocked GTX 285 card (while I wait for my back-ordered C1060) and the bandwidthTest is giving me some great results, except for the Device->Host transfer. My numbers for pinned memory are:

H->D: 5704 MB/s
D->H: 1490 MB/s
D->D: 120700 MB/s

Note that the D->H number goes to 2335 MB/s when I enable write-combining. I have a Lenovo Thinkstation D10, with PCIe x16 2.0 and the latest BIOS installed, running XP64. I’ve read a couple of other posts attributing this behavior to chipsets and/or BIOS… does this mean I am stuck with these results on my current machine? Has anyone resolved this lopsided bandwidth issue?