Problem with ActionMailer

Hi,

after installing actionmailer it ran well and i was able to send mail.
but after restart its giving the following error:

NameError in TestController#sendemail
uninitialized constant ActionMailer
RAILS_ROOT: ./script/…/config/…

Application Trace | Framework Trace | Full Trace
C:/InstantRails-1.5p1-win/InstantRails/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:266:in
load_missing_constant' C:/InstantRails-1.5p1-win/InstantRails/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:452:inconst_missing’
C:/InstantRails-1.5p1-win/InstantRails/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:464:in
`const_missing’
#{RAILS_ROOT}/app/models/notifier.rb:1

Ruby Experts please help me to resolve this issue.

Thanks
Kiran