firewall

i am setting a linux box as a squid cache server and a firewall. I used linuxconf to do the configuration.

under firewall, i enabled all the services except
1. forwarding rules and
2. outputting rules

after everything, i connected the linux box to my network to test it.

i pinged and got this message:

PING: SENDTO: OPERATION NOT PERMITTED
PING: WROTE 192.168.1.238 64 CHARS, RET=-1

THE IP NUMBER IS FOR MY LINUX BOX.
can somebody help me.