As you might know, there has been some issues with maintenance plans in sp2. Since the initial release of sp2, there has been released a later sp2, and also some hot-fixes. I won't go into details here, because Bob Ward from Microsoft has explained this much better than I can do. So, for background, details, build numbers etc, check out:

 http://blogs.msdn.com/psssql/archive/2007/04/06/post-sql-server-2005-service-pack-2-sp2-fixes-explained.aspx