CERN caching proxy problem

Dear Friends,

I have a CERN caching proxy running on a sun ultra sparc machine. The 
proxy server is bounded to the port 82 of that sun machine.  A 
Livingston Internet Router with dial-in facility is also connected to 
the network. This Livingston router does support IP filtering. We use 
this feature to set up IP filters on each dial-in port of the router. 

As a policy a http request on port 80 is restricted to the local 
network. That means if a http request is made on port 80 for any 
other web server out side the local network it is blocked by the 
Livingnston IP filter. However if the dial-in user wants to access 
any other web site he/she can send a request to port 82 of our 
caching proxy server.

This set up works with any browser as long as the users browse the 
internet. However if  a file is down-loaded through a web page the 
browsing session gets hang on. But this doesn't affect on the dial-up 
connection. It retains perfectly but transmission does not contnue.   
Is this a bug or something wrong with my configuration file. But the 
same file can be properly down-loaded  without going through this 
caching proxy server provided that IP filters are not imposed to 
restrict htttp requset on port 80.

Can anybody enlight me on this issue immediately.