If you are using the same net used by many others then there is a good chance that it is being shaped, so that people using P2P networks don't use up all the bandwidth. Also there is a chance that your ISP has started blocking P2P or specifically Limewire. As far as I know more and more ISP's that use satellite distribution for their internet have started shaping or blocking P2P usage.

I would suggest that you have a talk with the net supervisor in your building about how to get Limewire through, but just know that chances are that he'll say that, because of the high usage you are not allowed to use it anymore.

If he on the other hand doesn't mind then ask him to try and forward a port for you, (some high port in the 50000-65000 range eg. 64049) and then change your numbers in Limewire to the same number. You will need a static IP on your computer as well. This will also need to be done in cooperation with your supervisor, since you don't know what settings he has on the router.

These are instructions on how to set up a static IP

http://www.portforward.com/networking/staticip.htm