When assigning puppet classes through the "Edit Host" or "Edit Hostgroup" menus the little plus sign ( + ) does not appear, making it impossible to assign classes this way.

In /var/log/foreman/production.log we can see that Foreman somehow concatenates two paths while trying to load the picture for the plus sign button, as a result it cannot find it.

Excerpt from the log:

ActionController::RoutingError (No route matches [GET] "/assets/twitter/bootstrap/assets/twitter/bootstrap/glyphicons-halflings-2851b489e8c39f8fad44fc10efb99c3e.png"):
/usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:92:in `process_request'
/usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:118:in `run'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:65:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:in `safe_fork'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:58:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:41:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:159:in `spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
/usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
/usr/lib/phusion_passenger/passenger-spawn-server:61

The path should be: /assets/twitter/bootstrap/glyphicons-halflings-2851b489e8c39f8fad44fc10efb99c3e.png

Additional information, as requested:

OS: Debian 6.0.6 Squeeze, 3.2.0-0.bpo.4-amd64
Packages: foreman 1.2.0+debian0.2, foreman-mysql2 1.2.0+debian0.2, foreman-proxy 1.2.0+debian0.2

(the foreman packages were downloaded and installed through the package manager, "deb http://deb.theforeman.org/ squeeze rc")