site responding slow via linux proxy

Hello all,

I have encounetred a very strange issue on linux, i am using linux squid as proxy to access websites, while searching in a CRM site ( in asp.net ) i got slow response, without firewall access time is just 5-6 seconds and in proxy it increase to 40-60 seconds.
I check all possibility like with centos 4/5, with squid/ httpd forward proxy and changing kernal tcp parameters but no success.

Then i tried it with ISA Server on Windows and it responds well.

I also do tcpdump but nothing strange there,

 

Any errors in your logs?

 

really no error in logs,
do you have any idea of debugging it?

 

Unfortunately not...