I'm not much in the know about proxies either. But perhaps this might work:
http://www.gnutellaforums.com/showth...threadid=33712
It's not unusual to hear that one or some can connect on a school campus.
OK so we know that from your exact location that port 6346 is not being blocked. My next question is are you actually connecting via the school network or are you connecting independently. (Nvidia is your video card - do they also make modems?) What i mean is are you plugging into the school network via an ethernet card or are you using dial up or is there a separate modem device you use to connect with?
As far as Java goes, you should have at least Java 1.4.2 & not 1.4.1 Not a bad idea to update your Java.
Java 1.5 (take the JRE) Lw will certainly run better with it.