You need to play around with your block placements, see what works best. I have a site getting over 45K visitors per month and I think in April I earned only 5 Euro, which was really bad for the amount of traffic I was getting. So I started to play around with the ad blocks, changed the size or the placement. On July 5 (This Month) I took out two of the banners and replaced them with just 460X15 and 728x15 text links, I also changed the text from blue to red. While this is still a W.I.P. I am starting to see results, see the graph below,, remember it's euros and not dollars. Also when I took out the 728x90 learedboard banner from showing adsense, I was able to sell it here on DP for 1 month for $10. I am still working on this, but since I made the changes in the last few days, I do see a good improvement. I reckon I have moved from 5 euro per month to 25 euro per month plus $10 for a banner sale. So you see, you need to work at it,, never give up...