I am very new in Rails. after I created a new rails project.
rails new test project
I ran
rake db:create
In
I'm using Snow Leopard, had a similar problem recently. It happens that, for some reason, a system update created a hard link at /usr/bin/rake, pointing to OSX default 1.8 ruby environment rake executable. My 1.9 ruby installation is at /usr/local/bin, which comes later on my PATH setting, so when I ran "ruby -v" I got what I expect, same with "gem environment", but rake tasks were failing in the way you describe.
I just deleted the entry /usr/bin/rake. Moving /usr/local/bin up on PATH might've worked too. The result of running "which rake" must point to your 1.9 installation.
Hope it helps,
-- José