#step 1: open your 'sources.list' from: Places>Computer>etc>apt>sources.list
then remove everything and paste these lines:
deb http://repo.kali.org/kali kali-rolling main contrib non-free
deb-src http://repo.kali.org/kali kali-rolling main contrib non-free
#step 2: get everything clean and get update, upgrade and distribution upgrade with these command:
apt-get clean && apt-get update && apt-get upgrade && apt-get dist-upgrade
