When people suddenly have a connection problem after updating or upgrading LW, deleting the preferences folder is often the fix.
After you deleted the prefs folder, did all of LW's options revert back to defaults? If not then you know that the folder wasn't deleted properly & so try again. Remember that LW has to be properly closed first, otherwise the prefs folder won't be deleted.

I guess you have a wireless connection to the router? Is the router anywhere nearby so that you could have a look at it & find out the model number?

There are links for downloading older LW versions here: http://www.gnutellaforums.com/mac-os...link-here.html

Your port test worked, so looks like your school's not blocking gnutella's default port... can other people at school use LW or other apps using the gnutella network (FrostWire, BearShare, Phex, Morpheus, GTK etc)?