Internal server error

Passenger encountered the following error:

The application spawner server exited unexpectedly

Exception class:

Passenger::Railz::ApplicationSpawner::Error

Backtrace:

#	File	Line	Location
0	/dh/passenger/lib/passenger/railz/application_spawner.rb	182	in `start'
1	/dh/passenger/lib/passenger/railz/framework_spawner.rb	270	in `handle_spawn_application'
2	/dh/passenger/lib/passenger/railz/framework_spawner.rb	263	in `synchronize'
3	/dh/passenger/lib/passenger/railz/framework_spawner.rb	263	in `handle_spawn_application'
4	/dh/passenger/lib/passenger/abstract_server.rb	317	in `__send__'
5	/dh/passenger/lib/passenger/abstract_server.rb	317	in `main_loop'
6	/dh/passenger/lib/passenger/abstract_server.rb	168	in `start_synchronously'
7	/dh/passenger/lib/passenger/abstract_server.rb	135	in `start'
8	/dh/passenger/lib/passenger/abstract_server.rb	112	in `fork'
9	/dh/passenger/lib/passenger/abstract_server.rb	112	in `start'
10	/dh/passenger/lib/passenger/railz/framework_spawner.rb	87	in `start'
11	/dh/passenger/lib/passenger/spawn_manager.rb	218	in `spawn_rails_application'
12	/dh/passenger/lib/passenger/spawn_manager.rb	213	in `synchronize'
13	/dh/passenger/lib/passenger/spawn_manager.rb	213	in `spawn_rails_application'
14	/dh/passenger/lib/passenger/spawn_manager.rb	122	in `spawn_application'
15	/dh/passenger/lib/passenger/spawn_manager.rb	247	in `handle_spawn_application'
16	/dh/passenger/lib/passenger/abstract_server.rb	317	in `__send__'
17	/dh/passenger/lib/passenger/abstract_server.rb	317	in `main_loop'
18	/dh/passenger/lib/passenger/abstract_server.rb	168	in `start_synchronously'
19	/dh/passenger/bin/passenger-spawn-server	46