How to debug a HRESULT: 0x80131047 compile error

So I have this web project that I downloaded and for some reason it wont let me compile. Gives the error:

The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)

I know all the common reasons for that. Special characters in the path, etc. I check that, and did a LOT of googling. All of the answers point to special characters in the path except:

Unity application block 2.0 - The given assembly name or codebase was invalid

Which doesn't help because this is not a runtime error, but fails to compile.

I need to know how to debug this? How can I tell what assembly is causing this error because there are literally hundreds and there is no way I can just do process of elimination.

Screenshot:

You can increase the verbosity of the build under Tools -> Options, Projects and Solutions -> Build and Run. Then view the contents of the output window (View -> Output, Show output from: Build). With any luck the antecedents of the error are in there. You can also try running MSBuild from a developer prompt.