Could be that you have been smartpriced based on not enough of your clicks on ads converting for the advertiser.
Can you give us the link to your webiste... Possible that advertisers have changed and they are now giving less $$$/click Maybe you changed your content a bit and other ads are displayed ?
Why bother? You'll probably end up being banned judging by your other thread. http://forums.digitalpoint.com/showthread.php?t=122008