This is similar to issue 125246 which is now closed.
In SSMS (on a SQL Server 2008 CU4 machine), if I rename a stored procedure in the object explorer, the stored procedure is renamed fine and can be called properly via other stored procs, queries and so on.
The problem is that when I query the sys.objects/sys.sql_modules, the definition of it has the OLD name for the CREATE PROCEDURE.
My server is running on a WinXP SP3 machine (SQL Server 2008 Enterprise Evaluation). My client machine is a Windows Vista SP1 machine.