EXECUTE Permissions Denied - .NET and SQL2008 Compatibility Mode 100

We recently began testing our new SQL2008 servers running in Compat mode 100 and one of our .NET applications has stopped running and returning the error:

The EXECUTE permission was denied on the object 'My Stored proc', database 'My Database', schema 'dbo'.

Now I have already made sure that the login this application is making the connection on has the proper EXECUTE rights granted so I know that is not the issue. So I was wondering if there was any other c开发者_运维知识库ause that could be making this happen related to the compatitiblity mode of SQL Server 2008, or even something else?

The .NET application is currently in 3.5 and using System.Data.SqlClient to call the stored procedure.

Thanks in advance!

Figured it out - the user account I was using needed the appropriate EXECUTE rights (even though I specifically said I had done that). In Management Studio it did not tell me that when I granted these rights it was not sticking and when I right clicked the database and went Properties > Permissions and found the Effective permissions for the account in question I discovered the stupid mistake. This account originally came over from a SQL2000 instance and I just forgot to port the permissions over.