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 your LW isn't connected properly, please post your details.
System details - help us to help you (click here)