upgrade to rails3, but grip is broken

Gemfile

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+# Edit this Gemfile to bundle your application's dependencies.
+source 'http://gemcutter.org'
+
+gem "rails", "3.0.0.beta"
+
+gem "liquid"
+
+# http://github.com/merbjedi/mongomapper
+gem "mongo_mapper-rails3", :require => "mongo_mapper"
+#gem 'grip'
+
+gem 'warden'
+gem 'devise', "1.1.pre"
+
+## Bundle edge rails:
+# gem "rails", :git => "git://github.com/rails/rails.git"
+
+# ActiveRecord requires a database adapter. By default,
+# Rails has selected sqlite3.
+# gem "sqlite3-ruby", :require => "sqlite3"
+
+## Bundle the gems you use:
+# gem "bj"
+# gem "hpricot", "0.6"
+# gem "sqlite3-ruby", :require => "sqlite3"
+# gem "aws-s3", :require => "aws/s3"
+
+## Bundle gems used only in certain environments:
+# gem "rspec", :group => :test
+# group :test do
+#   gem "webrat"
+# end