I have banging my head for days now with this one so any help would be greatly apreciated. Below is an old post that another person had posted with the same problem / symptom as mine however no resolution. I now have this exact same problem ... please help.

I am running a squid server behind a firewall.
Problem is the network slows down to a crawl. Including
web traffic and traffic within the full network. The network
becomes ok when i remove the squid box from being pluged in.
I can surf the internet with the squid box, but it is so slow
that many pages timeout and clients get disconnected.

This problem only happens when I have the firewall port 8080 redirecting to the squid ip address If I stop forwarding the ports the problems stops.

My current config consists of a fully up to date centos 5.2 command line server with squid 2.6 something I believe. Squid box plugged in and the network has a high level of traffic, unplug the squid box the network is normal.

Please help.