Can not ping VPN Client after ICF is turned on

Hi all,

I have our remote web server connected to a VPN router in the office. The
remote web server is running Windows 2003 server. Everything is fine if the
Interent Conneciton Firewall is not turned on - I can ping from one side to
another, and can access files, browse network. Now if I turned on the ICF on
the remote server side, I am able to ping from the office LAN to the remote
server, but can not ping from that server to Office machines. Meanwhile an
error appears in the event log every time we try to log into the web server
with domain account:

Windows cannot determine the user or computer name. (The system detected a
possible attempt to compromise security. Please ensure that you
can contact the server that authenticated you. ). Group Policy processing
aborted.

Also the office computer is no longer can see the remote server through
computer browser, although it can connect it by direct typign \\SERVER-NAME.

I have all the ICMP enabled at the client side. What i need to do to make it
work?

Thanks,

Jack