A couple of weeks back a major Microsoft AdCenter bug costed advertisers huge amounts. This bug made the advertisers pay a blasting amount as compared to what they have bid for. However, this bug was soon fixed and before the advertisers could even raise their brows they were paid back.

However, a WebmasterWorld thread now reports that Microsoft have refunded advertisers by excess amounts.

I had 1400-ish bucks in incorrect clicks. They credited my CC the $1400, even though only $400 had been actually charged to my card. So, then they charged my card $1000 to even it out. They did give me a $200 ad credit for the trouble–which was cool.
THEN, they charged my card another $2000 in mystery charges that even they haven't figured out yet.
Pretty frustrating,
I'd advise everybody to go over your invoices carefully.

Well, we were overcharged by about $4k, and then we were credited by about $8k, and then they took back the over-credit, and supposedly TODAY they have it all right. At least, that's what the guy who called me said. I'm going to have to have my customer call his credit card company to be sure. What a mess.

First the advertisers were over charged. Microsoft accepted the fault and refunded then they charge them again. This situation sounds amusing, however, this might be far from amusing for the advertisers.