It may be the type libraries are not being updated.
If you write code in 2000, and reference the AutoCAD 2000 type library, it might be looking for the AutoCAD 200o type library and not updating to the correct one. i.e. AutoCAD 2007.
I can check the code on AutoCAD 2007 if you like, but you will need to pm me for an email address to send it to.