This is a heads up type of post...  I had a problem when I upgraded from 
Ruby 1.6.2 to 1.6.4 (the stable snapshot) - my Ruby script would core dump 
immediately.  I traced it down to the require of a .so created from a C 
extenstion - ruby was core dumping in the require of the shared lib.  So, 
I moved the current .so to a different extension (just in case) ran 'ruby 
extconf.rb' over again to create a new Makefile and did a make.  After 
that the core dumping problem disappeared.

So, the lesson is that if you've created C extensions and you upgrade your 
Ruby to a newer version, chances are you'll have to rebuild the shared 
libs for your extension.

Phil