Here's a quick tip for those who use Ruby support in NetBeans. By default NetBeans uses bundled JRuby. It currently comes in version 0.9.8 and there can be some issues when running more complex applications because JRuby is not 100% compatible with native Ruby yet. Also when you use Rails, new JVM is started each time you use a generate command with JRuby, which is pretty slow. Tor promised this be fixed in the future, however there is a solution now available.
If you want better performance and stability you can switch from default JRuby to native Ruby. Just install Ruby (which you probably have anyway) and set the Ruby binaries inside NetBeans to the Ruby ones instead of JRuby.
The drawback of course is that you're using Ruby so you can't take advantages of some of the features of JRuby (calling Java code from Ruby and vice versa). But if you don't need that, Ruby can be a better option for you - at least at this very moment when JRuby is not in final version yet.