Has anyone used the new Subassembly Composer?

My recent attempt at creating my first subassembly appears to have failed. The assembly looks and acts OK in the Subassembly Composer, but when I import the subassembly to the tool palette and add it to my assembly, I get an error "Net subassembly project, module, or class not found".

Is this a path thing? DLL thing? There are a bunch of files listed under the path shown under the subassembly's property on the tool palette.

Any suggestions?

Scott