VS 2015 Update 1 had big problems on one of my machines.
This was helpful: How to restore Visual Studio 2015 after the Update 1 (dependency dance)
A MS engineering guy has a full solution (basically a new devenv.config): here
Visual Studio 2015 Update 1 woes
Published Tuesday 26 January 2016
Previously: NDC London link dump (19 Jan 2016)