RestClient/ w/Cygwin

Trying to use rest-client with a small Ruby script under Cygwin, … it
works just fine on my dev VM & another VM I built, but it will NOT work
on a production machine:

$ irb
irb(main):001:0> require ‘rest-client’
LoadError: No such process - /usr/lib/ruby/1.9.1/i386-cygwin/

Using ruby 1.9.3p392 (2013-02-22) [i386-cygwin] on all systems, … have
looked at the Ruby & Cygwin configs, nothing appears pertinent. Tried
adding RUBYLIBS to env, no help; can’t be a compile issue, as Ruby on
the working system has not been recompiled [and looks like it cannot at
this time].

Any pointers to isolating this issue would be GREATLY appreciated!!!