Not able to access one special website

I am using squid3 as our proxy server.

Now we (all PC in the network) has issue to access VirginAustralia.com.au. I can open main page, but when I click "Find Flights", It is shown the following:

============================================
"The following error was encountered while trying to retrieve the URL: http://book.virginaustralia.com/Search.aspx


Read Error

The system returned: (104) Connection reset by peer

An error condition occurred while reading data from the network. Please retry your request.

Your cache administrator is webmaster.
"===========================================

In our squid configuration, we don't have block list for any website or IP.

Besides of cleaning the squid cache, anything else I can do? like add the URL to bypass the squid?


Here is squid3 access log:

1334531062.970     17 192.168.8.3TCP_MISS/200 677 POST http://www.virginaustralia.com/json/submission/findFlight.json - DIRECT/123.200.150.148 application/json
1334531062.990  18020 192.168.8.3 TCP_MISS/000 0 POST http://book.virginaustralia.com/Search.aspx - DIRECT/202.77.136.98 -
1334531063.002      7 192.168.8.3 TCP_MISS/502 4385 POST http://book.virginaustralia.com/Search.aspx - DIRECT/202.77.136.98 text/html
1334531063.806    746 192.168.8.3 TCP_MISS/502 4117 GET http://book.virginaustralia.com/favicon.ico - DIRECT/202.77.136.98 text/html