After installing IE7 on XP Pro SP3 workstations, communication between SEP MR3 client and the SEPM is lost. This is specifically in an environment using a proxy server.
Throw Internet Exception, Error Code=997;AH: failed to end request...
HTTP returns status code=404
Several possible issues:
Use HTTP 1.1
Use HTTP 1.1 through proxy connections
Connections key is recreated at reboot
Also, it may be needed to disable the IE functionality if "autocaching" see the following article for information from Microsoft: