Redmine

Hello,
I use nginx-extras with passenger from dotdeb repository on Debian x64.
Redmine works fine, but I can't upload files ex. images - every time I get 500 Internal Error page.

I have in nginx.conf:

user www-data;
(...)
passenger_root dir_to_passenger;
passenger_ruby dir_to_ruby;
passenger_max_pool_size 10;
passenger_default_user www-data;
passenger_user www-data;

and in redmine vhost:

passenger_enabled on;    
passenger_use_global_queue on;
rails_spawn_method smart;

Redmine app folder is owned by user-redmine (user and group).
Folders:
- files
- log
- tmp
are owned by www-data (the same like nginx and passenger) and chmod to 755.
Of course, I resterted nginx and redmine app (using touch restart).

What am I doing wrong?