If you try to install Primstar-2-dev-nnn.zip from a filepath that contains non ascii characters,
then the blender installer will fail (at least on windows).

  1. copy the Primstar-2-dev-nnn.zip for example to c:\tools (1)
  2. Tell the add on installer to install from there

(1): Of course you can choose any directory you like as long as its path only contains ASCII characters

I am not sure when the bug appeared first. But it has been reported on blender-2.57b