Error 0x8024401B

I have a server with a ISA server 2000 installed on it and 2 cards, External
and Internal, although i have done the following tasks but i can not update
windows and i gives me the above error

the tasks that i have done
* defined the sites needed for updating windows in isa server and letting
any requtest use it on isa server
* defined the sites needed for updating windows in IE security section as
trusted sites

i don't know why the authentication couldn't be done.
any idea?
Thanks

* starting windows installer in services in control panel
* Clearing the IE cache


erver. but
when my internet explorer proxy connection is set to isa server(which is the
server itself) i get the error 0x8024401B, and when i unset the proxy
connection in IE to nothing i get the error 0x80072EE2.