Sinatra Gem install error

I have been trying to install sinatra in a macbook running leopard system, and I am not able to do it. I get the following error.

MacBook:rubygems-1.3.7 lakshmanan$ gem install sinatra
WARNING:  RubyGems 1.2+ index not found for:
http://rubygems.org/

RubyGems will revert to legacy indexes degrading performance.
Bulk updating Gem source index for: http://开发者_JS百科rubygems.org/
ERROR:  While executing gem ... (NoMethodError)
    undefined method `gems' for #<Array:0x101901008>

Please help. I reinstalled gems also. Still I get the same error.

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rubygems.org does not seem to be responding right now. Try again later. It's probably nothing on your end.