pow says: Bundler::GemNotFound: Could not find rake-0.9.2.2 in any of the sources

I guess you updated RVM and run into this known issue: https://github.com/37signals/pow/issues/271

the easiest solution is to run it in project dir:

rvm env . > .powenv

OR:

cd /project/path # with .rvmrc
rvm env > .powenv