Folder tools are a useful feature for displaying and sorting data in table-formatted forms. However, I experienced a lot of problems with folders in an upgraded R12 environment. Especially when custom folders are opened by default in forms, users couldn't even close the form because of the repeating error messages. Needless to say this caused some frustration.

The solution was to remove the folders in System Administrator (Application > Administer Folders). We decided to remove the folders in the 11i environment before the final R12 conversion.