Green_Grass - 8:59 am on May 13, 2011 (gmt 0)
It seems your site has been flagged and clicks are being discounted. You may have to go in for a redesign and improve content to ad ratio. I would suggest immediate action before Google goes in for more drastic measures. In the past it has been seen that a dramatic fall in earnings is normally followed with a ban email after a few days. You have received a warning and have taken minimum action. This is not really what they would expect. My 2 cents.