Hi,
when you installed, did you burn the disk at the SLOWEST POSSIBLE SPEED, or if you used a USB stick, did you FULLY FORMAT it to FAT32?:
Do you have your software sources download location set to "Main"?:
You can try running this terminal command (Ctrl + Alt + t) if you think you have a broken install:
sudo apt-get install -f
I hope it helps!. 