Any thoughts on why the removeExistingCompletedJobs Method suddenly stopped working around March 2015? I'm not sure if it coincided with Spring '15 release or not as I wasn't watching closely. Code done by another developer bit over my head with the Cron stuff but I understand it a little.

I know there are other ways to remove scheduled jobs but this had been working fine for past 18 months. Classes are using API 31.0.

Submitted a case but Support hasn't been too helpful since this is in Production so I had to comment out code as a workaround (uncommented here).

    global void execute(SchedulableContext SC){
    queryBalance();
 
  removeExistingCompletedJobs(sc);
  scheduleNewJobs(sc);
 
  //Schedule a new batch to retrieve Existing Assignments
  startBatchToRetrieveAssignments();
 
  //Schedule a new batch to mark assigments as approved or rejected
  startBatchApproveAssignments();
 
  startBatchToDeleteHit();
}

//=========================================================================//
//Find new jobs and schedule them in the Queue
//=========================================================================//
   for(Schedule__c schedule :lstSchedule){
     schedule.Schedule_Job_Name__c = getJobName(schedule);
     schedule.Schedule_Job_Created__c = true;
    
     MturkScheduleJobPoster  mturkJobPoster = new MturkScheduleJobPoster(schedule.ID);
     **Id jobID = System.schedule(schedule.Schedule_Job_Name__c, getCronExpression(schedule),
                   mturkJobPoster );  
     schedule.Schedule_Job_ID__c  = jobID;**           
   } 

public void removeExistingCompletedJobs(SchedulableContext SC) {
   List<Schedule__c> lstSchedule = [SELECT Name,  Schedule_Job_ID__c
                                    FROM Schedule__c
                                    WHERE Schedule_Job_Completed__c = true
                                    AND  Schedule_Job_ID__c != null
                                    AND  StartDateTime__c < :System.now()
                                    Limit 100];
  
   for(Schedule__c schedule :lstSchedule){
       System.abortJob(schedule.Schedule_Job_ID__c);
       schedule.Schedule_Job_ID__c = null;
       schedule.Schedule_Job_Completed__c = false;
       schedule.Schedule_Job_Created__c = false;
       schedule.Schedule_Job_Name__c = null;
   }
   update lstSchedule;  
}