I think you got it backwards Orion hehe, he said he can get people connected to it from outiside of his network, but not from inside the network.
Which is definitely an odd situation, it's usually the reverse. But for internal network use you don't want to DMZ the machine. Some routers prevent internal networks from seeing a DMZ'd machine and it opens up everything on the machine to external which is never a good thing. Just forward the port you are using to it.
Also make sure your internal machines are using the internal ip, not the external. Some ISPs / routers, can't loop back onto themselves if you try to access them internally from the external address. If you really need to have the same address used in all places, go to no-ip.com and get a free no-ip domain, run the client on your computer so it auto updates your ip, and use that free domain to connect to it (pretty sure eqbc should be able to connect using a domain instead of an ip address).
Dev