Try these fixes from Birdy.
Are you connected properly (how many green connection bars do you see)?
If your connection is ok, try this:
Problems with the search
And if that's no help, 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 kill all of your settings within options, you'll have to go back through afterwards & reset things.
If there's a connection problem, please give us your details.
System details - help us to help you (click here)