PDF Signatures - Error Message

When signing a PDF signature field component, results in the following 3 error messages after each other (text correctly shown, spaces and all)

1) The FieldMDP expression for this signautre is invalid

> After clicking on OK on 1), i get the next err message

2) Creation of this signature could not be completed.
Unknown error
Support Information: CSigField-1013

> After clicking on OK on 2), i get the next err message

3)The document could not be signed.
There was an error when attempting to commit this signature. The document was not saved.
The save operation was cancelled.


Any takers?

Thanks in advance for any help