Redmine

reader,

my goal is to setup redmine. so to install rails , rubygems should be installed. while installing rubygems-0.9.4 following error raises !!!!!!!!!!!

hook /mnt/Downloads/ApplicationDownload/rubygems-0.9.4/./post-install.rb failed:
           private method `specification_version=' called for #<Gem::Specification:0xb7d923b8>

my configuration of ruby is - ruby 1.8.4 (2005-12-24) [i386-linux]
redmine version is redmine-0.7.0_RC1

i also try to install older version rubygems-0.8.11 and it is done but while executing 'gem install rails'
it show's

/usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:92:in `load_specification': private method `specification_version=' called for #<Gem::Specification:0xb7d8e460> (NoMethodError)
from /usr/lib/ruby/site_ruby/1.8/rubygems/specification.rb:421:in `initialize'
from (eval):3:in `load_specification'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:128:in `eval'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:92:in `load_specification'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:128:in `load_gems_in'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:127:in `load_gems_in'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:81:in `from_gems_in'
from /usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:53:in `from_installed_gems'
... 9 levels...
from /usr/lib/ruby/site_ruby/1.8/rubygems/remote_installer.rb:12
from /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
from /usr/lib/ruby/site_ruby/1.8/rubygems.rb:112:in `manage_gems'
from /usr/bin/gem:10

please guide if you have idea !!!!!!!!!!!!!!!