Rails - Jun 2009 - ArgumentError (interning empty string)

Hello,

I am trying to send an email out on registration for confirming and I
am thrown this error. I am unable to understand as nothing is nil in
the class which I am passing to the Mailer. Please do help me. The
stack trace follows:
ArgumentError (interning empty string):
  app/controllers/accounts_controller.rb:103:in `register''
  app/controllers/accounts_controller.rb:43:in `register''
  /usr/lib/ruby/1.8/mongrel.rb:159:in `process_client''
  /usr/lib/ruby/1.8/mongrel.rb:158:in `each''
  /usr/lib/ruby/1.8/mongrel.rb:158:in `process_client''
  /usr/lib/ruby/1.8/mongrel.rb:285:in `run''
  /usr/lib/ruby/1.8/mongrel.rb:285:in `initialize''
  /usr/lib/ruby/1.8/mongrel.rb:285:in `new''
  /usr/lib/ruby/1.8/mongrel.rb:285:in `run''
  /usr/lib/ruby/1.8/mongrel.rb:268:in `initialize''
  /usr/lib/ruby/1.8/mongrel.rb:268:in `new''
  /usr/lib/ruby/1.8/mongrel.rb:268:in `run''