Visual Studio 2013 HRESULT: 0x80131515; HRESULT: 0x80070057

I have a WCF web app that has been building and running under debug until Yesterday. The problem started when I decided I wanted a Release build to deploy. The Release was unable to build because of the

HRESULT: 0x80131515

involving Newtonsoft.Json.dll. But then at the end of the day, I lost power to my computer while Visual Studio was running. Now today, I am getting the same error involving the AjaxControlToolkit.dll instead! But this time it is worse. Trying to build the Release still creates the previous error code for the AjaxControlToolkit. The debug will still compile, but the page can't run properly and I receive this error from IE:

Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG))

I have tried,

1. Clean and Build the solution and each project individually.
2. Unblocking the files (files weren't blocked)
3. Downloading and replacing the AjaxControlToolkit.dll file
4. Clearing the C: \ Windows \ Microsoft.NET \ Framework \ v4.0.30319 \ Temporary ASP.NET folder
5. Clearing the C:\Users\user_name\AppData\Local\Temp folder
6. Restarting the computer
7. Reverting Git to a previous build into a new folder

Nothing has helped.

I would be happy to provide any more information. Thank you!

I think that the problem has either been solved... or is hiding for another day. Either way, I can now compile in both debug and release mode!

I was running Visual Studio Professional 2013 Update 1.
I am now running Visual Studio Professional 2013 Update 4.

Not what I would call a satisfying conclusion... But it works!