Are you pinging the IP address or the web site address (eg.
www.google.com)? If you are pinging the IP address and it works. Try pinging the web site address. Double check your DNS settings. SYSTEM -> NETWORK CONFIGURATION
Also, in the PROXY -> CONFIGURATION, check the section "Inter-Zone traffic setting".
Check the "Allowed Subnets per Zone". Make sure your subnet is in the BLUE box.