Can you create a procedure ? (and then modify it ?)

For example, can you run this ?
Code:
IF OBJECT_ID('dbo.spx_test') IS NOT NULL
	DROP PROCEDURE dbo.spx_test
GO

CREATE PROCEDURE dbo.spx_test
AS
BEGIN
	SET NOCOUNT ON;
	
	SELECT NEWID() AS New_ID
END
GO

ALTER PROCEDURE [dbo].[spx_test]
AS
BEGIN
	SET NOCOUNT ON;
	
	SELECT NEWID() AS New_ID
END
GO

DROP PROCEDURE dbo.spx_test
GO
I'm thinking that you don't have the correct permissions. When you backup (from 2000) and recover (to 2008), you probably lost the "connection" between the users that are on database level and the users that on SQL Server level.

You probably have to remove the users at the database level, and re-add them.