Rails 3.0.0.rc1 update - issue w Bundler 1.0.0.rc.1 and ruby 1.9.2.rc1

I upgraded my rails 3 version (now using bundler-1.0.0.rc.1 but bundle install in my test_app raises an error :

bundle install Fetching source index for http://rubygems.org/ Using rake (0.8.7) ... Using railties (3.0.0.rc) Using rails (3.0.0.rc) Updating .gem files in vendor/cache /Users/yves/.rvm/rubies/ruby-1.9.2-rc2/lib/ruby/1.9.1/rubygems/package/ tar_input.rb:111:in `initialize': No metadata found! (Gem::package::FormatError) ...

what could be wrong on this fresh install ?