On your business object make sure you've set the "PrimaryKeyIsAutoIncremented" property to False. By default SF sets this to True.
-Larry
BusinessLayerException An error occurred while saving an the data to the server.DataLayerSavingException Operand type clash: uniqueidentifier is incompatible with numericSqlException Operand type clash: uniqueidentifier is incompatible with numeric
Source : MicroFour StrataFrame Business
Am I doing something wrong ?