Outlook Custom forms Problem

I am having a couple of problems with an Outlook custom form, it started when I created a custom form in Outlook 2000 that allows staff to book leave via there manager which in turn places an appointment item in to a public folder on an Exchange sever 2000. the form works fine for users and managers the problem comes when the manager logs off at the end of the day, Outlook hangs and the manager has to Ctrl Alt Del to shut it down, I have checked and re-checked that all objects are set to nothing after use, I even re-created the form from scratch 3 times and each time the problem re-occurred but at a different stage, and every time I am unable to step back the program so it works again.
I am beginning to think that the after numerous publishing’s the forms are becoming corrupt, the only problem with this theory is that we have recently started using Outlook 2002(XP) and the original form works fine, I know the easy answer is to upgrade all to Outlook XP but with 4000 plus users this a little expensive.
What I am really looking for is conformation of the problem although a solution would be great.
Sorry if I have gone over board with the length and tech speak of this question but has been driving me mad
Dave UK

 

At any point was any iteration of your custom form modified and/or published on a workstation running Outlook 2002?