This error message relates to an illegal character for the Correspondent. Correspondents cannot include any special characters - a good rule of thumb would also be to ensure that there are no extra spaces after any words in the fields when in Correspondent Maintenance.
If you come across this error message, follow the steps below:
Open Main Case Handling/Proclaim Desktop.
Open the case where the error message occurs.
Navigate to the General Details screen or Client Details screen.
Click on Update and double-click on a field that relates to the correspondent, e.g. First Name.
Click on Maintain.
Ensure all fields are filled in correctly - special characters cannot be used.
Click on Update.
Exit the case and try again.