Is your connection ok? How many green bars do you see?
You said you'd used LW before without a problem but have you used it a dorm before successfully? Lots of schools & student accommodation are anti-p2p.
Do you see the firewall icon?

You could try deleting the preferences folder while LW's closed (points 2 & 3 below)
Fixes for LimeWire

If that doesn't help, check your roomie's LW settings & make sure yours are the same.