Unity Editor fails to load after 5.4.2f2 upgrade

I have just upgraded unity to Version 5.4.2f2 and now the editor fails to load completely. I have tried re-installing it twice and removing the licence files. It just winds down and becomes a do-nothing app in the background and that’s it. I have given it hours to try and figure out how to start up to no avail.

It was working great up until this morning when I upgraded to ver 5.4.2f2. Now it gives me the welcome screen, allows me to select a project, gives me a window that says it needs to import the old project into the new format and then just sort of dies silently. It is still in the Task manager but it is running in the background using no CPU. I tried just letting unity run for an hour to see if it would somehow open up the editor window but it doesn’t.

I have tried redoing the license and the other helps listed in the troubleshooting section on this website and no help thus far. Any help here?