0x80131040 error at runtime on an included project

Following a move away from Desktops and onto Terminal Server machines, I'm having to recompile a number of projects created by my illustrious predecessor at the company.

One of these projects is a fairly simple WPF MVVM project, with an error-reporting component added as a referenced project, i.e. the reference is to the project, not to a DLL. Both of the projects were started in earlier versions of Visual studio, but both now target framework 4.0 and are being maintained in VS2010.

The whole thing compiles fine, but at runtime I get the following error:

Could not load file or assembly 'companyName.Tracer, Version=2.0.0.0, Culture=neutral,
PublicKeyToken=0156bfd00d8c2368' or one of its dependencies.
The located assembly's manifest definition does not match the assembly reference.
(Exception from HRESULT: 0x80131040)

The referenced project is signed with a .pfx file, though I have tried compiling with and without the signing, and it appears to make no difference.

I'm not sure where "Version 2.0.0.0" is coming from. The referenced project is at开发者_JAVA技巧 version 1.1.* and the main project is also at 1.1.*.

Presumably I'm missing something obvious, or I've failed to include some vital piece of information, so I'll try to respond to any requests for additional information as quickly as possible.

Try to remove dependency, recompile DLL project with 4.0, and finally put the dependency back to the first project. It worked for me sometimes...