Can't connect to internet via ethernet

So I was playing Xbox360 using my ethernet cord, and then went back on my macbook and put the ethernet cord back in that. But when I went to connect to the internet it said that the Cisco Clean Access Agent could not connect or something like that. I'm at college btw. Oh and if you're wondering how I am posting this, I can connect via wireless which is very confusing.

When i try to use ethernet it gives me an ip address and everything and says that I am connected in the network preferences. However as said above I can't connect to the Cisco server. Thank you!

Please help!! I really don't want to have to take it to the tech. department at my school because they will for sure have it at least overnight and I kinda need it for school work.