There are certain keywords with which the harvester can't give any result, when used with proxies (I am using free proxies). For instance, I am giving the harvester the keyword "sony music" inurl:node. When I type it in google I am getting results, when I am trying to harvest without proxies I am getting results as well, but when I am using proxies I am getting no results. These are certain keywords that have this problem. When I am using others the harvester works just fine. How can that be explained and how could I solve it?