I can only assume that you have full access to your squid.conf file? Mine's in /usr/local/squid/etc/squid.conf. Look for the lines that begin with acl allowed_hosts src....
I have this, which allows my local network in:
acl allowed_hosts src 192.168.1.0/255.255.255.0
You can also look in your logs/access.log to see what in the heck is going on, too.