My solution: set https://accounts.google.com as a trusted site.
- Open the control panel
- Go to network and control
- Go to Internet Options
- Open Security Tab
- Click Trusted sites
- Click the "site" button
- copy & paste https://accounts.google.com to "Add this website to the zone" and click Add button
Now it worked for me. But if I removed this site, it still works. That puzzled me a bit...