Custom_require.rb:21:in `require__': no such file to load --

My application give me Error 500 and I get this in Apache log.

/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in
`require__’: no such file to load – initializer (LoadError)

from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in
`require’
from /var/www/myapp/public/…/config/boot.rb:16
from /var/www/myapp/public/…/config/environment.rb:10
from /var/www/myapp/public/dispatch.fcgi:21

I can find an istance of initialize.rb in my system at this address:

/usr/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/

I have the feeling I must set some PATH … but I dunno where :expressionless:

Advice ?

Simone