I'm having an issue with logging into Kali Linux.

This evening I installed the latest version of Kali Linux (2016.2), after I downloaded it from the original site. The installation went perfectly, and Kali was installed on a seperate partition alongside windows 10. But after I logged in as root on the GUI login screen, the screen turns grey and I cannot move the mouse cursor anymore.
Until now, I managed to log in 1 time (I didn't do anything special, just pure luck I guess, but after that I never accomplished it anymore). If any of you guys could help me, I would be so happy, because I'm very desperate and really don't know what to do. I already wasted a few hours googling with no result.

Thanks in advance!!!

Some facts:

- I bought my laptop just 1 day ago, and windows 10 was already installed.
- Video card: NVidea Geforce GTX 960M
- I installed Kali on a 40GB partition of my SSD

If you want to know anything other about my system, or the steps I took, please ask!