Addin only works on Outlook 2003

[Shane van der Westhuizen via OfficeKB.com]

Hi there

I'm new to developing addins. I'm using visual studio .Net 2003. My addin
works perfectly on Outlook 2003, but if I try and install it on Outlook
2000 or 2002 the button appears on the toolbar but the application itself
does not open when I click this button.

Please help

Shane