no clue sorry, but trust me man, its not worth any money, im one of the few here that even thinks about touching vb6 anymore, so they asked me at a certain point, till I saw that shithole xD
the "old" engines relied on that function, but since the event system, npc's are basically the things you attack, and all other stuff is done with events, they are so much more powerfull then npc's
make sure you have no ingredients etc set to 0, that would also cause that error.
also, we asked for a screenshot of the editor, please provide that so we can look if we spot something
is it that hard to ask that in google?
https://www.google.com/search?q=.net+framework&sourceid=ie7&rls=com.microsoft:en-US:IE-Address&ie=&oe=