Yes, I upgraded my Windows 8.1. I have installed few versions of .NET, including v3.5 and v4.0 I've tried changing .NET versions in NexusClientCLI.exe.config, but it didn't really help. When I changed supportedRuntime to "v3.5", installator told to install .NET v3.5, which is already installed (I tried to install it manually, but its installer doesn't even start). When I changed supported to "v4.0" or "v4.0.30319", I got error CS1703: "An assembly with the same identity 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' has already been imported. Try removing one of the duplicate references." And I couldn't find solution for this problem.