And you're sure you have 3-5 green bars at bottom left corner of LW?

If same problem again tomorrow let us know. I wonder if it's isp related. AT&T right?

Other than that, might be as suggested, something wrong with the U.P.'s you are connected to not responding to the search messages & passing them on to other ultrapeers.

Possibly, .. go to view menu -> Show Hide Connections window. Find the Ultrapeer you have been connected to for the longest, select it & press remove button. Wait a few minutes for LW to both find another & to settle its connection because you will lose connection momentarily. Then after a few mins try a search again.