did you turn off anti aliasing? That is what fixed it for me. Try the Cat 3.9's too, they are specifically suggested for running this demo.
Abit NF7 2.0/Nforce2 v3.13
Mobile 2600+ @ 2.76ghz/1.91V
Thermalright SP97 heatsink w/ Enermax 90mm
2 x 512 PC3200 Mushkin 222 Special @ 11-2-2-2/2.9V
BFG 6800 GT @ 430/1.14 // Soundblaster Audigy 2
WD 40 GB, 8MB // LiteOn CDRW
Antec SX635BII case // Antec Truepower 480
Vantec Nexus 3.5" Fan Controller // 5 x 80mm case fans
Win2KPro SP4
3D'03 : 12,807
http://service.futuremark.com/compare?2k3=2829028