If you are using Java 1.5 then you must be using OSX 10.4 right?
Port 6346 is being blocked by something. The question is what. It could be your software firewall, or more likely your router or ISP (internet service provider.) Since this all of a sudden happened, then it sounds like your ISP to me. Unless you changed something with your router/modem or osx firewall.

1. OSX Firewall settings for Tiger (click on this blue link)

2. We need to know what modem &/or router you are using ... what brand & model.

3. Who is your ISP?

4. Try this, go to LW's preferences, Advanced, Firewalls, change setting to Port Forward & change both connection & listening ports to 64049 & press apply. Then go to preferences, Connections & change to not connect automatically. Then quit LW. Then open LW, let is settle for 10 minutes. Then go to File menu, choose Connect. Give it plenty of time to try to connect.