I have three computers running on 12.04LTS, two of them I can use Ubuntu Tweaks to set up quick lists in Unity, but my desktop will not set up any quick lists.

Why not? Same operating system, actually the laptop and desktop are 64-bit and the netbook is 32-bit.

I am using version 7.3 Ubuntu Tweak on the desktop and I have tried and tried to to get it to work. What am I missing? Is there another app I need to make it work? If so I don't know what it is. All I know is that I was able to set up quik lists on the netbook and the laptop without any problems.