Redmine

After upgraded from 1.3 to 2.2, some javascript ui features aren't working anymore.
Here the messages I have on the Redmine Homepage:

Uncaught ReferenceError: Class is not defined 
Uncaught ReferenceError: warnLeavingUnsaved is not defined 

All the error seems linked to the Class is not defined.

Here my environment

Ruby version              1.8.7 (x86_64-linux)
RubyGems version          1.3.7
Rack version              1.4
Rails version             3.2.12
Active Record version     3.2.12
Action Pack version       3.2.12
Active Resource version   3.2.12
Action Mailer version     3.2.12
Active Support version    3.2.12
Middleware                Rack::Cache, ActionDispatch::Static, Rack::Lock, #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x7f86e7357530>, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, Rails::Rack::Logger, ActionDispatch::ShowExceptions, ActionDispatch::DebugExceptions, ActionDispatch::RemoteIp, ActionDispatch::Callbacks, ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, ActionDispatch::ParamsParser, ActionDispatch::Head, Rack::ConditionalGet, Rack::ETag, ActionDispatch::BestStandardsSupport, OpenIdAuthentication
Application root          /data/vhosts/o/xxxx.xx/redmine
Environment               production
Database adapter          mysql
Database schema version   20121026003537