Strange behavior of VS2015: Complains about "Strong Name Validation". Nothing helps

Environment: VS2015, .NET 4.5, .exe Console App + .dll@.NET 4.5 + other C++@CLR .dlls depencencies of my first .NET .dll

Everything was running fine, until I tried to move my project to .NET 3.5 and then back to 4.5. Since then on, VS2015 refused to run my app, although it does build succesfully in both .NETs. The reason:

{“Could not load file or assembly ‘TheAssemblyYouHaveReferenced’ or one of its dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A)”:”TheAssemblyYouHaveReferenced’}

I can't run it neither in win prompt.

Those must be other dependencies of my own .dll (that I've created and use it as reference.)

Check this: All of a sudden, also other VS2015 project that uses this problematic .dll exhibits exaclty same exception when I try to run that .exe With this other project, I did nothing, except that the shared .dll has been build in 3.5 and back to 4.5

Here is what I have tried to resolve it:

• I have signed all assemblies (referenced .dll and the .exe, which uses .dll) and rebuilt.

• I have switched off Properties->Build->Generate serialization assembly: OFF on all assemblies.

- I have used sn.exe to disable verification. This however, does not even work for some of the further dependencies. I.e. .dlls used by my .dll which are C++@CLR

- I also tried this link - No help ...

Now, I am clueless what do I do to bring the behavior of my VS2015 to the state before I compiled in .NET 3.5 and back to 4.5