Thats becuase you still didnt uninstall the old one, you just moved the apk file, its not that simple. Its still showing as installed though the apk is not there anymore, you need to follow the instructions from the first post.
The third line specifically is what you're missing. After this, it will install fine.
Question: On the Droid X...I installed the Cyan Live Wallpaper from the first page, which works perfect and looks amazing. What is the adb command to uninstall the wallpaper from the Droid X? I receive the same error as the guy above when I try to install a new live wallpaper.
Thanks!