gem install pg doesn't work on OSX Lion

Question

There are variations of this question bouncing around SO, but none of them seem to have an answer that solves my problem.

I am running OSX Lion (10.7.3). The latest

Answer 1

Rather than updating RVM itself (https://stackoverflow.com/a/10430742/2807795), as above, it was the reinstallation of Ruby 2.0.0-p247 that did the trick, after trying all the other steps above without success.

rvm get head
rvm install 2.0.0