Just because a user has been added to a DB does not mean that they have
permissions to do anything.  Either grant them EXEC permission on that proc
or add them to a role that has EXEC permission in the proc.

I have a sql 2005 database i can look the tables but not execute pro, i have
regsiter the users iwan and iusr in the database

Microsoft OLE DB Provider for ODBC Drivers erro '80040e09'

[Microsoft][ODBC SQL Server Driver][SQL Server]EXECUTE permission denied on
object 'res_vent', database 'centerplan', schema 'dbo'.

/resplanejados.asp, line 21

To add to Tom's response, you can grant a role (or user) execute permissions
on all objects on a schema with a single GRANT.  For example:

GRANT EXECUTE ON SCHEMA::dbo TO WebRole;

Note that it is generally best to grant permissions at the schema level only
when you don't need to be more granular.  If a principal needs access to
some objects but not others, individual object GRANTs are the best approach,
IMHO.  This is in contrast to a GRANT at the schema level and DENYs on
individual procs that take precedence over granted permissions.