I can only assume that the model you're trying to load is failing due to a shader or something. My polaris.x file which I created in AC3D, uses no shaders, and it loads, or seems to, into the Winforms demo.
The other problem is that until DGDK (C++) has a mechanism for error checking, the DGDK.NET version will not provide a way to check to see if a problem occurred when loading models. I can only suggest that you check to see if the file exists at the path you're specifying before loading the model in your program. It may be that the model isn't being loaded at all because the working folder is incorrect.
Paul.
Abundance = Choice = Freedom - Scarcity = Dependancy = Control, Truth!