I too ran into a lot of issues (right after the 1.5 release) where additional apps and even themes would not install after downloading. The issue was that the downloads were not complete. Go into your SD card and look for the liberty folder. Delete the contents in the download folder and try downloading again. I would recommend being on wifi as some of the packages are large. Another option is to download them directly from the links provided in the OP and load them from there.
Edit: By the way, this ROM is perfect. Can't imagine where they might go from here.
Edit: By the way, this ROM is perfect. Can't imagine where they might go from here.