Try the advice here:
all of a sudden will not connect (a fix to try)
Start off by deleting LW's preferences folder & changing Java versions.
You'll know if you've deleted the preferences folder properly...when you start LW, you'll go through the setup wizard again & all the settings within LW's options will have changed.
If you get confused with deleting the preferences folder, have a look at this post (Windows XP).
One bar, connection problems Vista Users: LimeWire Pref Folder in Vista
If nothing there helps, please give us your details.
System details - help us to help you -> Provide these details when you post!!!