I was able to find the solution, and the reason for the issue, in a response on the Apple Support forums:
I had no idea it would be scanning for other downloads. Armed with that, I went looking (for this, Spotlight actually worked). I found where we had copied her hard drive from her...
Okay...I give.
Somehow, my wife's e-mail address and account have infested my App Store (Mac OS X 10.6.8).
* I'm running App Store under my user account on the computer.
* It shows me as logged in.
* I have confirmed and re-updated my settings on the Apple ID website and through the...