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 ?

thfy