Mongo authentication error  #656

I am using gem mongomapper in my rails application. I have installed mongo and there is mongo router which managing different mongo instances. The schema which I am using in my rails application requires username and password to connect. when I am connecting this schema from mongo console I am able to successfully pass through but it fails when the same thing tries from my rails application. I am getting mongo authentication error. Here are the logs
/usr/local/rvm/gems/ruby-1.9.3-p374/gems/mongo-1.11.1/lib/mongo/functional/authentication.rb:205:in issue_authentication': Failed to authenticate user 'xxxxx' on db 'xxxxxx'. (Mongo::AuthenticationError)
from /usr/local/rvm/gems/ruby-1.9.3-p374/gems/mongo-1.11.1/lib/mongo/functional/authentication.rb:135:in add_auth' from /usr/local/rvm/gems/ruby-1.9.3-p374/gems/mongo-1.11.1/lib/mongo/db.rb:159:in authenticate'
from /usr/local/rvm/gems/ruby-1.9.3-p374/gems/mongo_mapper-0.12.0/lib/mongo_mapper/connection.rb:83:in connect' from /usr/local/rvm/gems/ruby-1.9.3-p374/gems/mongo_mapper-0.12.0/lib/mongo_mapper/connection.rb:89:in setup'`