Proxy timeout error

2009-11-11 16:42:16 EST pub.client:http 504 Proxy Timeout ( The connection timed out. For more information about this event, see ISA Server Help. )


Anyone experienced the above error on their IS hosting the TN.
Please share any experiences on the above as its been a recurring problem on our production servers and is eventually leading to the IS to loose threads and we have to re-start the server.

Vijay Kumar