[William Albert]

We're trying to deploy ISA Server 2004 as, among other things, a caching
proxy server. ISA is set up and working, and I've got the clients
automatically getting proxy settings.

This works fine for a couple of hours. After a few hours (even faster with
heavy use), Internet/Windows Explorer exhibits odd behavior (widgets
disappearing, text not showing up in dialog boxes, activity animation
centered at the top of the window, etc), Windows starts behaving erratically
(print spooler no longer works, can't bring up task manager), and the only
way to fix these problems is to reboot the client computer. If I remove the
proxy settings on the client and disable automatic configuration, these
problems go away.

I'm at a loss. I've seen Windows do some quirky things, but I've never seen
anything like this. There's no real common configuration among the clients.
Some still have Windows installs from the factory, some have been
reinstalled. Some are still running XP SP1, some have been updated to SP2.
And of course, nothing in the event log on either the client or server that
would indicate a problem. I don't even know where to begin troubleshooting.

Proxy Server:
ISA Server 2004 w/ SP1 Standard Edition
Windows Server 2003 w/ SP1 Standard

Clients:
Windows XP Professional (mix of SP1 and SP2).

Network is in an Active Directory domain. Proxy autoconfiguration
information is configured according to KB309814. ISA is currently acting as a
router that logs traffic. Firewall clients have been deployed and are working
correctly.