Status: 500 Internal Server Error when running mongrel

Hello everyone!
I try run simple RoR application, I go to RoR default "hello page",but I
got error, when trying to open new views.
Status: 500 Internal Server Error
  could not open database: unable to open database file
and so on, long list

my database.yml is default:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

But I am running almost the same configuration using Instant Rails
without any problems/
Has anyone met the same problem?

Have you installed SQLite3?