Try searching for some really old song that's not popular at all. Try using the All Types search too...does the same thing still happen?

Are you fully connected to the network?
Have you used LW before or is this your first try with it?
Delete LW's preferences folder when LW is properly closed. Points 2 & 3 below have instructions.
Fixes for LimeWire

You could try the 4.13.0 beta & see if the same thing happens.

Most of the time, this connecting/need more sources thing is because people are trying to download fake files (you've probably read about that...if you haven't, use the forum search to look for fake files) but every so often it turns out that someone can't download anything at all. I don't know why.