With Windows XP, Microsoft is continually updating the security measures, which impacts how the ProxySG manages patience pages.
If you are experiencing unexpected behavior with Patience Pages and Windows XP SP2, please refer to "Windows XP, Service Pack 2 Behavior" in the Configuration and Management Guide (CMG). For SGOS version 4.x, this is in Chapter 11: External Services, Section A: ICAP. For SGOS version 5.x, this is in Volume 7, Managing Content; Chapter 3: Malicious Content Scanning Services; Section B: Configuring ProxySG ICAP Communications. Simply search the PDFs for "WIndows XP, Service Pack 2 Behavior" and you will find the information. The CMG can be found at https://hypersonic.bluecoat.com/ .