Hi,
Ive had this message aswell. Worked hard to get all my credits and a few cars in my garage. So to make some credits I sold one on the Auction House and it went okay but when I went to get the credits for it, it kept saying transaction failed and then I started getting the "tampered with" message.
I have sent the e-mail to Forza as mentioned in the FAQ etc but not sure how long it takes, will have to wait and see but hope it doesnt take to long as I cant buy or sell new cars and thats part of the fun, getting the cars I need to race with. And I cant receive gifted cars from my friends either.
Anyone had this problem and may know how long it takes to resolve.. Would be grateful for any help
Thanks