Event Trigger Stopped working

[Thomasm]

I have a trigger that was creating an event based on the bid due date field.  The trigger still creates the event but now if i change the date it no logger moves the event to the new date.  Only thing that has changed was a similar trigger was created for another field, but i have deleted since this stopped working.  Here is my code

trigger createTask on Opportunity (before insert, before update)

{

        if(Trigger.IsInsert)

{

    List<Event> events = new List<Event>();

    List<Opportunity> Opps = Trigger.new;

                for (Opportunity Opp : Opps){

                                   Event evt = new Event(whatID = Opp.ID, Ownerid = Opp.OwnerID);

                evt.Subject = 'Bid Due Date for ' + Opp.name;

                        evt.StartDateTime = Opp.Bid_Due_Date__C;

                evt.EndDateTime = Opp.Bid_Due_Date__C;

                    Events.add(evt);

                }

                insert events;

                          }

if(Trigger.IsUpdate){

         Map<ID, Opportunity> OppMap = new Map<ID, Opportunity>();

                              for (Opportunity Opp : Trigger.new){

                                           if(Opp.Bid_Due_Date__C <> Trigger.OldMap.get(Opp.ID).Bid_Due_Date__C)

                      {

                       OppMap.put(Opp.ID, Opp);

                        } 

                       }

          List<Event> events = new List<Event>();

          List<Opportunity> Opps = Trigger.new;

          String Sub = 'Bid Due Date for%';

                    for(Event evt : [Select Id, Subject, WhatID, OwnerID, StartDateTime, EndDateTime FROM event WHERE WhatID IN : Opps and Subject like :sub])

          {

               Opportunity Opp = OppMap.get(evt.WhatId);

               evt.StartDateTime = Opp.Bid_Due_Date__c;

               evt.EndDateTime = Opp.Bid_Due_Date__c;

               Events.add(evt);

                }                 

Update events;

                  }                                    }

[Coco_Sdyney]

First check whether you could get any records from:

 [Select Id, Subject, WhatID, OwnerID, StartDateTime, EndDateTime FROM event WHERE WhatID IN : Opps and Subject like :sub]

add a line of system.debug to print out evt.size().