Constant Synthesis not found , rake Aborted!

I was trying to execute rake:migrarte . I am getting an error related to
Synthesis,

Given below is the out put.

E:…\trunk>rake db:migrate
(in E:/…/trunk)
rake aborted!
Constant Rails::Synthesis from rails/synthesis.rb not found
Constant Synthesis from synthesis.rb not found

Thanks,
shilesh.