Which version of LW 5 are you using?

Have you used older versions of LW before without a problem?

Try updating your Java: Java SE Downloads
Download the JRE offline installer & remove any other Java versions via Control Panel, before installing this one.

If that doesn't help then delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will change all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
Vista users: LimeWire Pref Folder in Vista