Make sure that you're only using 1 software firewall (more than 1 will cause problems) & that LW's being allowed through it.

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

In case you're using Vista: LimeWire Pref Folder in Vista

If nothing there helps, please give us your details.
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