I have a custom addin that runs code when the mailitem.send event is fired, however in certain cases the mailitem.send is not fired and it skips to the application.itemsend event and i don't know why.

Here's the scenario. Compose a new email click "send", mailitem.send event is fired but due to custom code it appropriately cancels the event. I then click "send" again, the mailitem.send event is skipped and the application.itemsend event fires. I don't want to have any custom code behind the application.item send. I can run the same scenario on different machines and only find the problem with one configuration but I can't figure out what it could be. This problems occurs on specific Windows XP/Outlook 2003 machines.

Any help would be apprecatied.