Expression Blend displaying error when creating sample data from an existing class.

Question

When I try to create new sample data based on an existing type, I get the following error message:

GetType cannot be called with null or empty typeName

I tried restarting Expression Blend 4, but without any success.

The type I am trying to use was generated by WCF RIA services, but suspect that shouldn't matter. I've used this feature quite a few times now and it's the first time it's doing this.