This happens when the user has added characters to a numerical field.
- Go to Site Explorer > Forms
- On the left-hand side, click on the Data tab.
- Find the user that submitted the form.
- Click on the name of the user.
- You should now see the form that was submitted.
This may occur if the user entered a number field, like social security, in an invalid form. For example, entering 3 digits of SSN instead of 9, and clicking Save, then navigating back to a previous step.