On your computer, do you have any other Filemaker products?
On your network, do you have any other computer running FMP products?
On your network, have you changed port forwarding on your router for any other computer?
I have Bento running on a different Mac on the same network. I have not done anything with ports on any computer.
How many computers are on your network?
Do you have an IT department?
A general overview of your setup would be helpful.
If you are on a small network, knowing your web IP address would be helpful.
http://whatismyipaddress.com don't tell us, just note it.
what is your local IP address (assuming your computer is hosting the database)
I am on a home network. I have an iMac, MacBook Pro, and MacBook in addition to assorted AppleTVs and Wiis. It also has an AE Extree and a couple of Expresses on it as well. I installed FCP on the MacBook which has been retired from active use so I plan to use it as a "server" of sorts to host the database 24/7 (currently it hosts my iTunes collection). I'm pretty sure I have a dynamic IP from Comcast, if that matters, which it might from what I've read on the forums.