VmWare Workstation Guest Is Not Pinging Host

Hi Folks.

Here is my scenario:

Host Os: Windows VistaEnterprise SP1
VmWare:Workstation V6.5.1
Guest OS:MSWindows2003server Enterprise Edition SP2

Problem Description:
I can ping from host to guest IP
Note: NAT is enabled in VMWare

I can not ping back Host IP from the guest OS..

Any possible resolution.. Urgent.