I got the following random error:
You receive a “The incoming tabular data stream (TDS) remote procedure call (RPC) protocol stream is incorrect” exception when using NVarchar parameters with Sqlclient
Its a known bug with the .Net SqlClient Data Provider. If you have a field in the database of type nvarchar(max) or greater than 4000 characters and if the user enters data into the field greater than 4000 characters via the .Net SqlClient Data Provider you will receive an exception.
To get around this, reduce the field size to less that 4000 characters or change your type to ntext or set the Sqlparamter.size property to -1 to allow the entire data to be saved.