My account was also similarly banned after posting a Payton Manning Card during the Ultimate Madden promo around Thanksgiving because my card sold for above the average price during a card shortage for that LTD at the time. Days later other cards sold for higher than mine but mine was banned because other cards were in the Auction house when someone bought mine. I got an email stating that after review they found they took the proper actions and I am still banned from the Auction house several months later since Thanksgiving. I feel robbed and not valued as a customer or player...its a shameful thing and disingenuous to the players...
Good luck and hope you recieve a different outcome. Please share an update if it gets resolved for you!