If the bug report's true then you shouldn't have a firewall problem... means that you can accept incoming connections. I don't know why direct connect's not doing it! Have you tried restarting LW? You could delete your preferences folder (when LW's closed), that seems to fix some weird problems. Points 2 & 3 here
Fixes for LimeWire
This will kill your settings within tools > options, you'll have to re set everything afterwards. Give LW a while to settle down & see what happens.

I really don't see why you would need to port forward but try it if you like! You should be right using port 6346. Just remember to set up a static IP address first.