When you built ruby 1.9.1 from source, did you go all the way to make
install? If so, what was the root (config --prefix=/???) that you
gave prior to the initial make?
I've found that just linking in the executable with major releases of
anything is often the shortest path to disfunction.
Here's a sequence you could use to build a parallel RoR suite.
1) Identify a new root for your RoR install suite like: /opt/RoR.
Create that directory and make yourself be owner (so you won't need to
sudo all the time).
2) In your Ruby source directory type:
2a) ./configure --prefix=/opt/RoR
2c) make install
You'll now have /opt/RoR/bin, /opt/RoR/lib, ... with your new ruby in
3) In a term window type:
3b) ruby --version You should see something like:
ruby 1.9.1p0 (2009-01-30 revision 21907) [powerpc-darwin9.6.0]
3c) gem install rake rack
3d) gem install rails
Now you've got a new RoR suite that's available if your path is
modified as in step 3a, else you've got your original RoR setup
(assuming you haven't already blown it away).