Run the following command line from the VS command line tools:
devenv.exe /?
This will show another command that may help, especially:
devenv.exe / safemode
Does it work in safe mode?
devenv.exe / log
,
devenv.exe/resetsettings
devenv.exe/resetaddin
devenv.exe/resetskippkgs
[edit] devenv.exe/log ....