I am working on year end processes and need to delete some zero records from a custom object.  I have written a trigger that will fire when a field on a custom object is set to YES for delete zero records.  The trigger appears to be working correctly until ready to delete the record.  I am getting the following error.

EXCEPTION_THROWN|[28]|System.DmlException: Delete failed. First exception on row 0 with id a0AJ0000005AY6fMAG; first error: ENTITY_IS_DELETED, entity is deleted: []
09:37:48.247 (1247331000)|FATAL_ERROR|System.DmlException: Delete failed. First exception on row 0 with id a0AJ0000005AY6fMAG; first error: ENTITY_IS_DELETED, entity is deleted: []

Here is the Trigger code:

trigger DeleteZeroOrders onStart_Budget__c (afterupdate) {

if(trigger.isUpdate)

{   

Start_Budget__c sb = [Select Delete_Zero_Open_Orders__c fromStart_Budget__c];

system.debug('Delete Open Orders = ' + sb.Delete_Zero_Open_Orders__c);

    If(sb.Delete_Zero_Open_Orders__c == 'Yes'){

List<Open_Order__c> OrdersToDelete = new List<Open_Order__c>();  

for(Open_Order__c o : [Select Id,Current_Year_YTD__c,Future_Year_YTD__c fromOpen_Order__c])

  {   

system.debug('Selected Open Orders = ' + o);

if(o.Current_Year_YTD__c == 0){

    IF(o.Future_Year_YTD__c == 0){

     OrdersToDelete.add(o); 

system.debug('Orders to Delete = ' + OrdersToDelete);    

  }

    }

    If(OrdersToDelete.size() != 0)

Delete OrdersToDelete;

  }

    }

}

}