Open root terminal and type this code.
leafpad /etc/apt/sources.list
Add all repositories
deb http://http.kali.org/ /kali main contrib non-free
deb http://http.kali.org/ /wheezy main contrib non-free
deb http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali-dev main/debian-installer
deb-src http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali main contrib non-free
deb http://http.kali.org/kali kali main/debian-installer
deb-src http://http.kali.org/kali kali main contrib non-free
deb http://security.kali.org/kali-security kali/updates main contrib non-free
deb-src http://security.kali.org/kali-security kali/updates main contrib non-free
apt-get update
apt-get upgrade