I think that some problems might be caused when a library gets
installed to both, perhaps with the wrong .so being loaded - not
sure.... Is this possible?
(My questions are towards ruby in general, but specifically towards the
Windows One Click Installer)
For all OSes, ruby/1.8/ holds the core and sandard libs --those that
are part of the Ruby distribution proper. And site_ruby/1.8/ holds 3rd
party libs.
Your OS package manager might install addiitonal libs in either of
these depending on it's own practices. (I wonder what they SHOULD do?)
Another potential directory for such things is ruby/gems/1.8/ which
stores libs installed via RubyGems.
T.