[Cura crashes on startup, Windows 7 Enterprise]

OK. I've been using CURA 3.6 for 4 months with no problems but as of a week ago it is crashing during opening. I've tried to reinstall and it is not helping.

I've also tried installing 4.0 now that it is official and it loads but has a blank GUI (The old beta version worked fine 2 months ago when I tried it briefly.)

[Ultimaker Cura 4.0 | Stable available!]

OK so when I first install 4.0 it opens successfully. After closing and re-opening it, however, it opens with a basically blank GUI. This is before installing any plug ins.