>I don't know. It is just when I set the value in the XML (again using my own serializer) and then (in the SQL Server SP) I try to get the value back, I get the error. It appears that the code in the SQL Server SP expects the separators. Why?, I don't know.

Your code:

SELECT @TargetDate = [Fld FldName].value('.','char(10)') ...

forces the result to be 10 characters wide, with no separators, there are 2 spaces trailers that would cause an exception. Simply use varchar(10) instead of char(10). If time might be included then that would be more than 10 or shifting would cause first character to be included, prefer something like varchar(20).