Today I renamed the sa account on 23 SQL Server 2005/2008 instances.  I used the CMS to assist with this task. 

Later we realized all of the SQL Agent jobs were failing on these instances with the following error: “The job failed.  The owner (sa) of job XYZ does not have server access.”

We use sa as the job owner, and it had correctly changed the owner to our new name as the sids had not changed.  We were at first confused why the jobs were failing but then realized restarting the SQL Agent service might help.  The restart corrected the problem.

If you plan on renaming your sa account (best practice), make sure you restart the SQL Agent service afterwards to avoid failing jobs.  This is perhaps common knowledge, but it was something new learned by me today.