I have two projects, `ProjectA` and `ProjectB`. `ProjectB` is a console application, which depends on `ProjectA`. Yesterday, everything was working fine, but suddenly today when I run `ProjectB` I get this:

> 
> **BadImageFormatException was unhandled**:  
> 
>  Could not load file or assembly 'ProjectA, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. An attempt was made to load a program with an incorrect format.
> 
> 
> 

Both are just regular projects, with no dependencies on any other non-.Net projects. Both are fully .Net - there is no native code, and no P/Invoke. I have other projects which depend on `ProjectA` and still work just fine.

Things I have tried:

* Make sure both projects are set to "Any CPU," with the *build* checkbox checked. They are.
* Make sure both projects are for the same Target Framework *(.Net 4.0 Client Profile)*.
* Under ProjectB --> References --> ProjectA --> Properties, make sure *"Copy Local"* is set to *"True"* \_ *(I verified that ProjectA.dll is being copied correctly)*
* Clean/Rebuild the solution. I even tried manually deleting the /bin and /obj folders in both projects.
* Restart Visual Studio. Restart my computer.
* Check out an entirely new copy of the repository.

But I still get the same error. I have no idea what I did to cause this, nor how to fix it. Any ideas?