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 109 in `spawn_application'
1 /dh/passenger/lib/passenger/railz/framework_spawner.rb 287 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 224 in `spawn_rails_application'
12 /dh/passenger/lib/passenger/spawn_manager.rb 219 in `synchronize'
13 /dh/passenger/lib/passenger/spawn_manager.rb 219 in `spawn_rails_application'
14 /dh/passenger/lib/passenger/spawn_manager.rb 122 in `spawn_application'
15 /dh/passenger/lib/passenger/spawn_manager.rb 253 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