Can't Ping public ip from TMG2010 Client

Hello,

I have a problem with ping public ip from TMG2010 clients, but i can ping public ip from TMG2010 server is ok and also ping TMG2010 server from my local lan is ok, problem is that when i was try to ping public ip from tmg client it's get time out request. I was also try to create firewall rules -internal/local host to External (ICMP/PING) and Network rules ..but fail to ping ...

I have two NIC cards configured at LAN 192.168.x.x /24 and External 10.0.x.x /24 as recommended by Microsoft.

So please can someone help me to solve this problem that i face last 2 weeks.

Thanks  

Tinku