Update and proxy question

[Bart Silverstrim]

The organization I'm in has moved to using what I believe is a Bess 
filter behind a PIX firewall, and it authenticates users before allowing 
access to http and https sites.  It tries to automatically authenticate 
users to a Windows Active Directory domain.

The boss said I can manually configure my web browser to use the proxy. 
  I set it up in Firefox to go to the correct port and address, and it 
prompts me to log in then I can web browse.  But auxiliary services...my 
weather applet, my system updates...are blocked still.  Even if I set my 
network settings to use that proxy and use authentication, the filter is 
blocking everything except for my Firefox browser.

Is there a client-side solution to this??