SQL Server job - execute step with a proxy account...

Question

All,

I'm attempting to execute a sqlserver agent job (sql-server 2008) which will execute a SSIS package via a proxy account.

I've completed the following steps:

1. Created a login for the AD account which will act as a proxy
2. Created a credential mapped to the above mentioned login
3. Created a proxy (with access to the Execute SSIS Subsystem) using the credentials above
4. Created a job, with a SSIS step to be executed as above mentioned proxy.

I'm receiving the following error:

Executed as user: xxxx. The process could not be created for step 1 of job yyyyy (reason: A required privilege is not held by the client). The step failed.

I then additionally added the login to the sysadmin group, but got the same results. Does anyone have any experience in doing this? I've followed a few guides (listed below) but still no luck.

1. http://msdn.microsoft.com/en-us/library/dd440761(SQL.100).aspx
2. http://msdn.microsoft.com/en-us/library/ms189064.aspx

Any help appreciated it.

BB