This RIA Services bug from MIX bits has been fixed but until new bits are released, watch out!
The MIX build of RIA services has a bug that has been fixed since. But you might experience it as I did this morning and go around in circles for a while. This blog post is to help you avoid wasting that time.
I normally create my model is in its own project and hadn’t seen this problem until this morning.
If you add a model into a RIA Services project (e.g., the web project created from the Silverlight Business Application template), you must build the project before you create a new Domain...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.