This error took me a while to figure out. I was using SqlDataSource with stored procedures for SELECT and UPDATE commands. The SELECT worked fine. Then I added UPDATE command and while trying to update, I would get this error:

"Procedure of function has too many arguments specified"

Apparently, good guys at .NET decided it is necessary to send SELECT parameters with the UPDATE command as well. So when I was sending the required parameters to the UPDATE sp, in reality, it was also getting my SELECT parameters, and thus failing.

I had to add the extra parameters in the UPDATE stored procedure and make them NULLABLE so that they are not required....phew...

Here is piece of SP with unused parameters.

Update: I was getting that error because unkowingly, I had bound the extra fields in my GridVeiw with Bind() call. I changed all the extra one's, which did not need to be in Update, to Eval() and everything works fine.