Did you launch SketchUp with the correct params to listen to port 1234?
https://github.com/SketchUp/sketchup-ruby-debugger

I never tried to set it up for Aptana, but I set it up for RubyMine. Posted some instructions here: http://forums.sketchup.com/t/please-help-me-to-setup-de-debugger-on-rubymine-for-mac/289/2?u=thomthom

Maybe some of that info is transferable.