This can occur when fields such as email or date fields have been renamed in the application. These fields are coded to require information in a specific format.
Locate the field that is causing the error and edit the description to ensure that the information entered will match with the format (date fields for dates, grad year fields for alumni information, etc.) If the application has been submitted, you will need to create a copy to make the changes. Once this is done, you can activate the new application and inactivate the incorrect one.