exception handling

Hi
    I have code in model as

def self.record_paginate_pb(search_pb_ui_hash,page)
problem_number=search_pb_ui_hash[:number]
problem_priority_id=search_pb_ui_hash[:problem_priority_id]
search_problem = self.find_where_options :order => 'created_on DESC' do

pb>

    pb.number1.downcase =~ "%"+problem_number.downcase+"%" if
!problem_number.nil?
    pb.problem_priority_id== problem_priority_id
  end
          rescue ActiveRecord::ActiveRecordError => e:
            puts 'error happened '+e.to_s
            else
          paginate search_problem.update( :per_page=>10,:page => page )
end
  and this is called from controller as
@search_pb_result=Problem.record_paginate_pb(params[:problem],
params[:page])

I am new to ruby's exception handling (learning)..How can I write a
rescue block for the above code ..I tried like above but is not
working..Could you please help me and also point to some good tutorials
on rails exception handling?

Thanks in advance
Sijo