Don't worry about the warning banner...that's just there to stop people from downloading infected files posing as LW updates.
The info doesn't apply to music, movies etc...just to LW updates.

Is your LW connected properly (all green/blue connection bars)? If LW's connected, try the fixes below.

1. In LW go tools > options > searching > basic & check whether the 'show license warning' box is ticked. If it does, untick it > Apply > ok...see if that makes any difference.

2. Problems with the search

3. 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 LW's options, you'll have to go back through afterwards & reset things to the way you like them.
Vista users: LimeWire Pref Folder in Vista

If LW's not connected, try the fixes here.
If LW Will Not Connect
If nothing there helps, post back with your system details