When running .NET apps, it you use "172.0.0.0" it treats the app as coming from the internet because it takes a very simple approach by looking for a period in the address. If it finds one then it "must" be from the internet. <g>
I meant to say 127.0.0.1 which happens to be your tcp/ip loop back. it basically represent your local ip address. every machine has this address. most firewalls will allow your machine to access itself - NIS does not. It's not that I'm using the ip address by choice - it just happens to use it if there is not other address available (i.e. when you're not connected to a network where you can get a dhcp address).
I found that to be a little strange - even more so when it wasn't logging it. .NET security was perfectly fine. I suspect that NIS was the culprit since it works fine since I reinstalled with default settings.