Bundler 1.0.13 (version released May 4, 2011) running with rubygems 1.7.2 issues this annoying deprecation warning:
NOTE: Gem::SourceIndex#all_gems is deprecated with no replacement. It will be removed on or after 2011-10-01.
Gem::SourceIndex#all_gems called from /Users/me/.rvm/gems/ruby-1.9.2-p180@composer/gems/bundler-1.0.13/lib/bundler/rubygems_integration.rb:256
A fix was committed on 5/11/2011 in the Bundler repo to correct an issue submitted 5/6/2011.
Pending release of Bundler 1.1, you can try this solution:
$ gem uninstall bundler
$ gem install bundler --version=1.0.12
I hope this helps. Took some digging to find it.