svn bindings error on 1.8.6

When calling Svn::Repos.create() and Svn::Repos.open(), I keep getting
this error. I'm convinced that i'm using the correct path to the
repository. I'm calling Svn::Repos.open() with a single argument, the
full path to the repository.

TypeError: in method 'svn_repos_open', argument 2 of type 'char const
*'
    /usr/lib/ruby/site_ruby/1.8/i386-linux/svn/util.rb:60:in
`svn_repos_open'
    /usr/lib/ruby/site_ruby/1.8/i386-linux/svn/util.rb:60:in `call'
    /usr/lib/ruby/site_ruby/1.8/i386-linux/svn/util.rb:60:in `open'
    /usr/lib/ruby/site_ruby/1.8/i386-linux/svn/repos.rb:29:in `_open'
    /usr/lib/ruby/site_ruby/1.8/i386-linux/svn/repos.rb:29:in `open'
    /var/www/html/TiddlyWiki/app/controllers/repo_controller.rb:118:in
`save'

The OS is fedora core 8

I'm trying extend acts_subversioned to save versioned columns to an
svn repository while keeping record of the versions in a database.

Does anyone have any advice on where I can get help / support using
the svn bindings for ruby?