Firewall client cannot ping to Public IP

My network connectivity is

Firewall Client / Web Proxy Client(10.0.0.10) - ISA server 2006 (10.0.0.25) - Cisco Router - Internet

I configure two policies

1. Ping from internal to local host - its working fine.

2. Ping from internal to external( internet) - this is not working.

Now ISA server can ping to internet and firewall client can ping to isa server, but firewall client cannot ping to internet

Regards,

Syed