'Error Evaluating Check Constraint'

We had the need to change a column in an Access 2007 database from a number format to a text format. Once the change was made and somebody attempted to enter text into this field we would recieve the error 'Error Evaluating Check Constraint' After doing some digging around in the Field Properties I was able to find what was causing the problem.

In Field Properties verify the the Validation Rule is blank. Ours had a setting of >0. This was because the field was intially set as a number column that could not be 0.