I have had some odd things happen related to the creation and execution of maintenance plans. In general, I try to avoid creating and using them unless they perform file system maintenance operations like deleting old database backup files.

My suggestion is that in the future, you use T-SQL to script the maintenance you want to have happen and paste it into a SQL Agent job. Obvious choices for this would be:

1. DBCC CHECKDB

2. Database backups

3. Index maintenance operations

4. Updating of index statistics

I think you'll find that you have fewer mysterious problems.