Jobs in 9i does not start one day, 10g scheduler's surprise!

Problem

I had ported the existing jobs in 9i to 10g. It was working properly for 2 or 3 months and one day the jobs did not work. I tried to reexecute them, it says it does not know the procedure in schemas. For instance, EXAMPLESCHEMA.mysampleproc('myparameter'); is not executed. So after some trials, like restarting the database but only omitting the schema name, solves the problem. I left the thoughts of why does it happen to later days.

But, because it is painful change the job definitions of hundreds of jobs, I preferred using job scheduler feature coming in 10g. Surprise is coming now: while defining the jobs in job scheduler, they did not start.

Cause:

No real cause, it can be misleading design bug.

Solution:

The only stupid reason behind was, setting the start time and next start date formula same time. In order to make it execute you must give next date apart from start time, they must not be same!