Question : Cannot ping external remote network

We have a remote site that  runs a biometric access terminal connected to the Internet on a broadband connection.
The records on the terminal are downloaded using software installed on a PC within the Head Office network (running SBS 2003 Premium).
To check connection I tried to ping the external IP of the remote site's router from the PC, but get the 'Request timed out' message.
I can ping the router from the server ok, and from my home, but not from the PC (even logged on as Admin).
We have had no problems with connection until a few days ago. The only possible changes may have been a windows security update (the user is not certain about this).
How can I enable the PC to be able to ping an external source.

Thanks for your time reading this.

Answer : Cannot ping external remote network

Can you confirm that the Watchguard also allow inbound echo-reply? This is the response that comes BACK from the other end. Most protocols don't need this as it is response traffic to an outbound request - ICMP DOES need it.

can you check the log at the remote router - does that see the ICMP request? What i am thinking (maybe) is that the ping is getting there but the response back is just being dropped.