Heh. If you get an IP address, they are probably just blocking your MAC addy when you first try to hit something on port 80 ( which is what teh web runs on). I get around similar all the time by tunneling all my traffic over ssh - port 22, almost never blocked - to my home machine and then a proxy on my home machine to the world. One of the folks in our ITS department does similar, but she says port 5000 upd is almost always open for credit card transactions, so she runs a VPN connection on that port back to work and connects that way.
Works great when you set it up on your box, then use a second card/address/alias to provide an open ad-hoc network to connect to
