Arielf,
Pienso que el problema es puertos seguros. Look at this:
# db configuration show squid
squid=service
EnforceSafePorts=no
SafePorts=21,70,80,81,119,210,443,563,980,1024-65535
TCPPort=3128
TCPProxyPort=80:3128
TransparentPort=3128
access=private
status=enabled
Apagado a los puertos seguros para 80:
db configuration setprop squid SafePorts \
21,70,81,119,210,443,563,980,1024-65535
expand-template /etc/squid/squid.conf
signal-event remoteaccess-update
Espero que esto trabaje.