[squid-users] can't open a page with squid

Hello list. I have a problem with squid and need some help with it.
My proxy is running in transparent mode and is working fine, but i
found out some user can't access a page.
If i remove the proxy from our topology the page can be accesed normally.
I'm running squid squid/2.6.STABLE5 on a debian 4.
You would probably tell me to upgrade to STABLE17, but can't find the
package with apt-get, should i download the sourcecode and compile it
?

IE browser give this message:
ERROR
The requested URL could not be retrieved

--------------------------------------------------------------------------------

While trying to retrieve the URL: http://mapa.buenosaires.gov.ar/sig

The following error was encountered:

Read Error
The system returned:

    (104) Connection reset by peerAn error condition occurred while
reading data from the network. Please retry your request.

Your cache administrator is federico.sarmiento@vinculomedico.com.

While firefox keeps trying to open the page.

Thanks.

-- 
Federico Raúl López Sarmiento.