Have you used LW successfully at school before?? If your port test failed to display the page, something's blocking LW's default port...possibly the school's not allowing access?? Lots of schools block p2p. Talk to whoever's in charge of the dorm's internet & find out whether you're allowed to use p2p. Can other people use LW in the dorm??

You could try changing ports. In LW tools > options > advanced > firewall config. Change LW's listening port to 64049 (or try others in the range of 49152 - 65535) > Apply > ok.

If you could connect at school without a problem until you upgraded to Pro, try this: Delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
LimeWire Pref Folder in Vista