Sales difference between Merchant and Tracking Software

[grafx77]

I currently have 4 merchants that I am reviewing on my affl. website. I have been lucky enough to talk one of my merchants (the highest paying) into placing an affiliate tracking script, from my tracking program, onto his "confirmation page" so that I can accurately track my PPC ads to sales.

From the time period of Nov. 16-31, my tracking program "Adwatcher" has tracked 15 sales. My merchants affiliate sales tracking app. "MyReferrer" has tracked 13 sales. No big deal......a few sales off, no sweat.

From the time period of Dec. 1-4, my tracking program has tracked 7 sales and my merchant has tracked only 2. I added yahoo ads to my arsenal on Nov. 31st, so this is the reason for my jump in sales and clicks. I have made the affiliate manager aware of this gap and am awaiting a response back tomorrow.

My question is.........Have any of you more experienced marketers who use an off-site affiliate script to track sales, through your tracking program, experienced a similar gap in sales? I would like to know if this is common or if it may be an error on the merchants tracking software or mine.

Any experiences are welcome.

John