MacOSX (10.7) vr Run Error

I installed everything like the site said with no errors, but when I
tried to run the program by entering “vr” at the command prompt I
received this message:

/Users/Castor/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in
require': cannot load such file -- rubygems/builder (LoadError) from /Users/Castor/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:inrequire’
from
/Users/Castor/.rvm/gems/ruby-2.0.0-p0/gems/visualruby-0.1.2/vr:15:in
<top (required)>' from /Users/Castor/.rvm/gems/ruby-2.0.0-p0/bin/vr:23:inload’
from /Users/Castor/.rvm/gems/ruby-2.0.0-p0/bin/vr:23:in `’

Also, I previously downloaded XQuartz, which opens when I issue the “vr”
command.

Thank you!