Error when importing a World Server package

I am receiving a package that I guess to be a world server package. It ends with the extension .wswz. I am using STUDIO 2015 SR2 release 12.2.5099.5 on a Windows 8 PC.

When i open the package i get an error when it starts importing the package Could not load file or assembly 'ICSharpCode.SharpZiplib.Version=1.0.6052.29101. etc.. etc..

I have attached the image of the screen

This was working fine until about two weeks ago.

Help ?

Ivan