Error 4401 - Unable to populate data, please check if mandatory value is entered correctly.

Error 4401 - Unable to populate data, please check if mandatory value is entered correctly.

I am getting the following error message when using the Zoho API

4401 Unable to populate data, please check if mandatory value is entered correctly.

Not sure why but here is URL that is submitted to the service

http://crm.zoho.com/crm/private/xml/Events/insertRecords?ticket=a416f097db7a2525ac32c93aebd6e59b&newFormat=1&apikey=dT5zMDWRPwrPFdBdNJfCFjJn2Gsh*57TkQaMGWeIdlI$&xmlData=<Notes><row no='1'><FL val='entityId'>335343000000042082</FL><FL val='Note Title'> Imported from Goldmine </FL><FL val='Note Content'>*** HAL ***  November 9, 1999 </FL></row></Notes>

I want to update the contact notes section. The entity code, apikey and ticket have all been triple checked. The xml format was taken from the documentation.

Help!