Are you using ICS? If so, I'm surprised you got it working. ICS is a headache in a box.
Theoretically, Windows shouldn't have a problem with multiple NICs. Are you getting DHCP through one NIC and static through another? If you could give more details on your setup, it would help a bit (static/DHCP settings, DNS, workgroup/domain, etc).
How happy is the blameless Vestal's lot!
The world forgetting, by the world forgot
Eternal sunshine of the spotless mind!
Each pray'r accepted, and each wish resign'd.