I have found that the One Click Installer sets an environmental variable
called RUBYOPT that points to the Ruby Gems library. This causes a
problem if a copy of the Ruby interpreter is run on the same computer
from a different folder than the original installation folder, since
Ruby Gems will not be found in a subfolder of that interpreter.
I have found that this problem can be solved either by clearing the
ROBYOPT variable, or by creating a file called ubygems.rb in the same
folder as the interpreter. Note that the initial ‘r’ is missing from
ubygems.rb. That file can be empty, that is, contain no executable code
(comments are o.k.). Apparently, the interpreter will look for this
file if the RUBYOPT variable is set, but only the existence of the file
is necessary for the main script to continue.
Hope this helps,