It's very strange. Could try making some restart, or trying to upgrade to 10.8.2 (if you don't have any cause not to upgrade). All the machine in office do the same behavior?
If it's only one you could also try to reinstall FileMaker...
I know : not so useful my contribute
I would check network configuration of the computer as well as the network components first (NIC, cable, router) first.
It is alll the machines in the office. I even put my laptop on their network, and found the same issue.
I found a fix, but still don't know why this became an issue.
I determined that, from the client's location, the web viewer can't resolve the 'local.google.ca/maps'" address, but can resolve "google.ca/maps".
I confirmed that Safari and Internet Explorer (using Parrallels on my MacBook Pro) also couldn't resolve the address from the client's location. They can get maps if they type the addresses by directly into the web interface for google maps. I could get the default address to work from my MacBook from a remote location.
I changed the address in the web browser from the 'default' for Google Maps (CAN) to a custom address using 'google.ca/maps' and everything works as it should again.