i checked the debian package of libgdk-pixbuf2-ruby and it contains this 2 files:
usr/lib/ruby/1.8/gdk_pixbuf2.rb
usr/lib/ruby/1.8/i386-linux/gdk_pixbuf2.so

and some others ..

the thing is that the ubuntu pkg dont contain these to file which are "vital" for the pkg to mean something .. none of the examples in the pkg work (because of this files)

bye,
httpdss