Maybe their systems picked up on some fraudulent clicks -- like one person clicked your ad 10 times so they removed those clicks.

I was talking with a friend about Adsense, and he had some kind of software on his computer that was accidentally clicking on his ads until he realized and got rid of the software. Then 1 year later Google emailed him about it and took the money out of his current month's earnings. I think it was $8. :rolleyes: