installing home brew for rails 3.2 - osx-lion

Question

I am trying to install homebrew according to the guidelines described in here.
I have curl and rvm, and want to install rails 1.9.3 on my lion 1.7.4 with Xcode 4.3.2 and with developer command line tools installed.
It seems I will need libksba, which requires me to use to command brew install libksba.
So I will need Home Brew.
I follow the instructions and use
/usr/bin/ruby -e "$(/usr/bin/curl -fsSL https://raw.github.com/mxcl/homebrew/master/Library/Contributions/install_homebrew.rb)"
which outputs the following:
$ /usr/bin/ruby -e "$(/usr/bin/curl -fsSL https://raw.github.com/mxcl/homebrew/master/Library/Contributions/install_homebrew.rb)"
==> This script will install:
/usr/local/bin/brew
/usr/local/Library/Formula/...
/usr/local/Library/Homebrew/...
Press enter to continue
==> Downloading and Installing Homebrew...
==> Installation successful!
You should run `brew doctor' *before* you install anything.
Now type: brew help
[~]$
[~]$
[~]$ brew doctor
/usr/local/Library/Homebrew/tab.rb:1:in `require': no such file to load -- ostruct `(LoadError)`
from /usr/local/Library/Homebrew/tab.rb:1
from /usr/local/Library/Homebrew/bottles.rb:1:in `require'
from /usr/local/Library/Homebrew/bottles.rb:1
from /usr/local/Library/Homebrew/extend/pathname.rb:2:in `require'
from /usr/local/Library/Homebrew/extend/pathname.rb:2
from /usr/local/Library/Homebrew/global.rb:1:in `require'
from /usr/local/Library/Homebrew/global.rb:1
from /usr/local/bin/brew:10:in `require'
from /usr/local/bin/brew:10
[~]$
So this means basically that brew was not installed right. Do I have to change the path at which it is looking for? I used to have MacPorts in, which I completely erased so there should be no conflicts there. Please help!!! Thanks a lot! It's an awesome community.
UPDATE:
I time machined back a year because I thought I did something critically wrong. Now I still have an issue installing, but it seems a bit more common.
I installed homebrew using
/usr/bin/ruby -e "$(/usr/bin/curl -fsSL https://raw.github.com/mxcl/homebrew/master/Library/Contributions/install_homebrew.rb)"
Any command of "brew" gives me this error:
[~]$ brew
/usr/local/bin/brew:6:in `require': no such file to load -- pathname (LoadError)
from /usr/local/bin/brew:6
Any suggestions? Thank you all!

Answer 1

I had the same problem as mentioned in my comment above. To resolve it I ended up having to restore my default system ruby. I am on SnowLeopard - OSX 10.6.8, so your resources may vary, but what I did was:
uninstall xcode: sudo /Developer/Library/uninstall-devtools --mode=all
rsync or copy /System/Library/Frameworks/Ruby.framework from another machine running 10.6.8
You also need the ruby executables in /usr/bin to point to the system Ruby: /usr/bin/{erb,gem,irb,rdoc,ri,ruby,testrb}
these are just symlinks to /System/Library/Frameworks/Ruby.framework
erb -> ../../System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/erb
so I re-symlinked them, for example from /usr/bin: sudo ln -s ../../System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/erb ./erb
the brew executable currently uses /usr/bin/ruby so that needs to be there in the least
I hear future versions of brew will point directly at the system ruby on the /System/Library/Frameworks/Ruby.framework path, so symlinking ruby to a custom install is a bad idea
At this point brew commands worked again and ostruct (part of ruby standard lib) was again found. I went ahead and added xcode back in and worked through some minor 'brew doctor' errors.
I have now replaced all my old macports packages with homebrew packages and its such an improvement!