I have what should be the exact same card, and I am having the exact same problem.
Strangely, I think XFX makes the 6800Xtreme AGP from 2 different chips. Yours is obviously an NV41, But RivaTuner lists mine as an NV42. XFX lists 2 apparently identical model #s, UDE3 and VDE3, which one do you have?
Everything looks right in Riva, there is one pipe quad disabled and one vertex disabled. I enable the xtra quad and vertex, but after I Restart it still lists 8pp and 4vp as Current, however, in the same line it lists 12pp, 5vp as Target. I too have HW mask listed as N/A. It seems I did everything right, but it's not switching on Restart
Check out these relevant guides:
1. Has anyone else had this problem with the HW mask N/A?
2. Has anyone heard of the NV42 chip or know what other models it's used in?
which model #s, UDE3 and VDE3, which one do you have?