I have a custom GP tool that I've written in C# for 10.1. I've compiled it, registered it, used it to build a model, and it runs it desktop. Now I want to publish it as a GP service. I go through that process and it publishes. But it won't run as a published tool. I get the 816 error stating that it's not valid. I've validated it in model builder, I've analyzed it before publishing and those are all fine. What else do I need to do???? This model worked in 10.0 but not in 10.1.