Teamviewer 13 won't start on Win7 64bit

Hi guys,

I tried installing Teamviewer again after having setup my system fresh. Now no version will open the GUI. The service is running and I can see the Teamviewer process for a second in tast manager and then it crashes again. tried some older verison, same thing. I could install an old V6 I have. Tried uninstalling, cleaning registry etc to no avail. Any ideas? Thanks!

Best, David