Thanks Don!
FYTI: Sounds like your are using IIs 7.0
1) How is your PB application connecting to the WS (via EasySOAP / SOAP)?
- The key here is whether your application is using the pbwsclient120.pbd or pbsoapclient120.pbd library
2) Can you try turning off UAC altogether and see if that makes a difference?
3) What operations is your WS performing?