When I sold the site that I originally used to sign up for Adsense, the new owner's applied for adsense as their site. Google checked the information for the owner of the domain and saw that they were the owner.
At this time I had enough in my account to get it FedEx'd/UPS delivery but they weren't doing that back then.
Google sent me an email that I didn't end up receiving and because I didn't get right back to them, they disabled my account.
Terrified, I of course contacted them. They notified me that the original site that I applied with must be under my control or I am responsible for asking for another one to be approved.
I then submitted another site to them after explaining that I didn't receive the email, they approved the new site and re-enabled my account.
They were very kind about the situation, I received my check, no problems. Just was really alarming as I didn't understand why my account was disabled.
If you are going to sell the original site that you used to apply, submit another site for approval prior to the sale and transfer of the domain.