Right before I submitted the app (a second time) for review, I decided to ask the user if they wanted to upgrade to the full version every time they saved a bill...I forgot to also remove the buy button on the main menu, when a purchase was made in that particular instance. The user still got the full version, but as you can imagine, the presence of the buy button made it look as if the features were still unlocked.
I'm of course working on an update to fix those..and add a few new features.