Please note that Blender 2.50 to 2.56 do not work with Primstar. For Blender 2.57 and later you need Primstar 2.
The 1.0.0 stable release requires Blender 2.49a or Blender 2.49b and a full Python installation to match.
All Primstar releases including snapshots of the git repository for testing purposes and older releases are available in the release project page.