All of a sudden with the latest LW update, I couldn't connect anymore. What's up I ask? Sure enough, I visit this forum and many others are having the same problem all of a sudden. Well, going to the help links came up with a fix.
Go to your C:\Documents and Settings\ "your name" and you will find a folder labeled ".limwire"
Delete the folder. Problem fixed!
This fix is posted by limewire FAQs, that's where I found it and it worked for me.
Hope this helps.