Stuck on undefined method `downcase' for nil:NilClass

Anyone have encounter this problem ?“undefined method `downcase’ for
nil:NilClass”

run on port :3000 successful

Thanks in advance

[root@ public]# ruby dispatch.fcgi

Status: 500 Internal Server Error
Content-Type: text/plain

undefined method downcase' for nil:NilClass ../config/../vendor/rails/actionpack/lib/action_controller/request.rb:17:inmethod’
…/config/…/vendor/plugins/filter_logged_params/lib/filter_logged_params.rb:70:in
log_processing' ../config/../vendor/rails/actionpack/lib/action_controller/base.rb:378:inprocess_without_filters’
…/config/…/vendor/rails/actionpack/lib/action_controller/filters.rb:364:in
process_without_session_management_support' ../config/../vendor/rails/actionpack/lib/action_controller/session_management.rb:117:inprocess’
…/config/…/vendor/rails/railties/lib/dispatcher.rb:38:in dispatch' ../config/../vendor/rails/railties/lib/fcgi_handler.rb:150:inprocess_request’
…/config/…/vendor/rails/railties/lib/fcgi_handler.rb:54:in process!' /usr/local/lib/ruby/gems/1.8/gems/fcgi-0.8.7/lib/fcgi.rb:606:ineach_cgi’
…/config/…/vendor/rails/railties/lib/fcgi_handler.rb:53:in process!' ../config/../vendor/rails/railties/lib/fcgi_handler.rb:23:inprocess!’

*** LOCAL GEMS ***

actionmailer (1.2.2)
Service layer for easy email delivery and testing.

actionpack (1.12.2)
Web-flow and rendering framework putting the VC in MVC.

actionwebservice (1.1.3)
Web service support for Action Pack.

activerecord (1.14.3)
Implements the ActiveRecord pattern for ORM.

activesupport (1.3.1)
Support and utility classes used by the Rails framework.

fcgi (0.8.7)
FastCGI library for Ruby.

hoe (2.3.3)
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mysql (2.7)
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MySQL C API provides for C programs.

rails (1.1.3)
Web-application framework with template engine, control-flow layer,
and ORM.

rake (0.8.7, 0.8.0)
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rubyforge (1.0.4)
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