Segmentation fault debugging Ruby 1.8.4 in Eclipse 3.2

Fresh Eclipse 3.2 on MacOS X 10.4.7, latest stable Ruby Development
Tools plugin (…), Ruby 1.8.4 . As soon as I start debugging
even the most stupid Hello World file I get:

ruby 1.8.4 debugger listens on port 49657
/Users/…/test.rb:1: [BUG] Segmentation fault
ruby 1.8.4 (2005-12-24) [powerpc-darwin8.7.0]

I have read about other people getting segmentation faults, but none
doing something so simple. I would prefer sticking to 1.8.4 while
waiting for Rails to support .5 . Any idea? Thank you in advance,