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:inregister’
/usr/lib/ruby/1.8/mongrel.rb:159:in process_client' /usr/lib/ruby/1.8/mongrel.rb:158:ineach’
/usr/lib/ruby/1.8/mongrel.rb:158:in process_client' /usr/lib/ruby/1.8/mongrel.rb:285:inrun’
/usr/lib/ruby/1.8/mongrel.rb:285:in initialize' /usr/lib/ruby/1.8/mongrel.rb:285:innew’
/usr/lib/ruby/1.8/mongrel.rb:285:in run' /usr/lib/ruby/1.8/mongrel.rb:268:ininitialize’
/usr/lib/ruby/1.8/mongrel.rb:268:in new' /usr/lib/ruby/1.8/mongrel.rb:268:inrun’