Make sure the sources.list file contains only this:
Code:
deb http://http.kali.org/kali sana main non-free contrib
deb http://security.kali.org/kali-security sana/updates main contrib non-free
# For source package access, uncomment the following line
# deb-src http://http.kali.org/kali sana main non-free contrib
# deb-src http://security.kali.org/kali-security sana/updates main contrib non-free
Edit the /etc/default/grub file and add 'nouveau.modeset=0' to the GRUB_CMDLINE_LINUX line and then run update-grub2. Then reboot.