Google AdSense announced a new waiting period to validate that the leads or sales from your Google Referral ads have actually gone through. So all but Google specific referral ads must go through a "validation period" before you, as a publisher, can get paid your earnings for those leads and sales.
We've recently made a change to help make sure that the conversions generated by referral ads are valid. For some publishers who display referrals for non-Google products, the earnings you receive for the ad may now be less than the maximum referral value displayed for that ad. This is because our system will initially place a restriction on referral earnings as we monitor click and conversion data to determine that the conversions generated are valid. Once this validation period ends, you'll begin earning the maximum value of the conversions as displayed in your account.
There is a large thread at WebmasterWorld with mixed reaction to this announcement.