I am trying to publish my contacts in order to do a Google sync. However I keep getting this error

and I don't understand why. I do not have the option of not publishing these fields. "X_ID" is the key field and "prenom" is the first name field. Both of these fields are text fields. Initially the publish script refused "X_ID" because it was a number field and I thought it refused "prénom" because of the accent. Those issues have since been resolved but others have arisen. Any ideas what's wrong and how to fix it?
Geoff