Every machine in the house has a static IP address with a 28 bit subnet mask.

The 28-bit subnet mask might have something to do with it? Also, the server software: Has it been told to assign receivers an address range within that subnet?

That's pretty much it. The server is locked down, with most services turned off.

Could be one of the things you disabled. Are you doing any packet filtering on the server?

Incidentally, for personal firewall software, I highly recommend BlackICE Defender. It'll run on your server just fine.

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Tony Fabris