I’ve been working with the great Ruby Eclipse project (which if you haven’t played with, download and then go through the tutorial. It’s been working flawlessly on my XP Laptop, but I hadn’t been able to get it to work on my Linux box. Basically, with both 0.6 and 0.7 versions, I would go to Project->New->Ruby and would get an error that it could find the class org.rubypeople.rdt.internal.ui.wizards.NewProjectCreationWizard. There was very little info on the web about it, but I had a hunch.
I was running Eclipse 3.1, but it got to 3.1 bu /upgrading/ from 3.0. My laptop had a fresh install of 3.1. And sure enough, removing the 3.0/3.1 app files and running a fresh 3.1 install with the RubyEclipse plugin added worked like a charm.