What are the Worst Mistakes You can make (or have made) with Dynamics GP?

John Lowther and I are working on a presentation for the upcoming GPUG Summit and we are looking for the worst mistakes you can make with Dynamics GP. We have some of our own ideas but we would love to get more ideas from everyone else. If you've got a nasty mistake that you've made or seen with Dynamics please comment on this post or email me at mpolino@gmail.com.