*** Updated 6/1/2009 -- I've noticed that this post along with the contact selector demo are by far the most commonly viewed posts, therefore I added some "common things to look for" section towards the bottom***
What a lovely error this is. If you've been using SharePoint workflows you've probably come across this error; usually with a few tweaks an clicks, possibly a quick re-save of the workflow and voila, the error goes away. If you've searched the web for this error you will see that t...