Might be ORM problem

Hi,
I have a model user.rb, a controller userdata_controller, methods
in the controller and respective .rhtml files. I created a
registration page. Saved into users table and it works fine. But
sometimes its throwing error as

undefined method `city=’ for #

c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/
attribute_methods.rb:251:in method_missing' c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/ base.rb:2361:insend’
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/
base.rb:2361:in attributes=' c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/ base.rb:2360:ineach’
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/
base.rb:2360:in attributes=' c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.1.0/lib/active_record/ base.rb:2130:ininitialize’
app/controllers/matrimony_controller.rb:124:in new' app/controllers/matrimony_controller.rb:124:inuseraccount’
-e:2:in `load’
-e:2

It assumes that there is no field ‘city’ in table users.
I confused a lot. It is never working until i restart my mongrel. I am
not able to predict, when the problem rises.

Any idea? Help me…

Thanks,
-Sadeesh kumar.