If the installer installs the files into a privileged location (e.g. c:\Program Files under windows), the administrator rights for updating the repositories are not preset if the user start the updater without admin rights. 

Admin rights are currently gathered later in the process before doing any modifications to the file system. 

But to update the repositories to the ini file, admin rights are needed. This means, the admin rights should be gathered much earlier.  

So, one needs to run the installer with "run as administrator" to make it work.  After modifying the repositories once (and quit the installer), a newly started 
installer works without early admin rights.