Why does plugin install fail?

Neither…

ruby script/plugin install
svn://projects.jkraemer.net/acts_as_ferret/trunk/plugin/acts_as_ferret

…nor…

ruby script/plugin install
svn://projects.jkraemer.net/acts_as_ferret/tags/stable/acts_as_ferret

…work for me when I try to install the plugin: Is there a problem with
the code repository?

Thanks for your help!
Tom