Stored Procedures Permission Problem

[Sam Dean]

MySQL 5.0.18
VB2005 application with MySQL Connector/NET 1.0.7
My MySQL experience: over 5 years
My MySQL Stored Procedure experience: minimal

SP created as root@localhost. All relevant privileges granted as follows:
GRANT SELECT ON db.view_tablename TO username@’123.123.%.%’ IDENTIFIED BY ‘password’; ( matching grant on db.tablename also.)

GRANT EXECUTE ON PROCEDURE sp_procname TO username@’123.123.%.%’

FLUSH PRIVILEGES;

Security_type on sp_procname is: INVOKER

When username@’123.123.%.%’ runs the application the following error occurs: MySql.Data.MySqlClient.MySqlException: #42000 SELECT command denied to user ‘username’@’123.123.%.%’ for table ‘proc’.

I then grant the following privilege as root@localhost:
GRANT SELECT ON mysql.proc TO username@’123.123.%.%’ IDENTIFIED BY ‘password’;

Now the application works ok. I don’t see any documentation about needing to grant rights to mysql.proc. What is wrong here?