Go to Tax Tools > Tools, then 'Delete a Form' from the pop-up menu.
If you see "Adoptive Child Worksheet", "Adoption Carryover Computation Wksht", and/or "Form 8839" delete them all.
Start with the worksheet because they have to be deleted before the Form 8839 will stay deleted.
Then, close the program, and clear your Cache and Cookies before continuing.
@melissaprickett