I'm debugging an app, using the "Use alternative JRE" option. Anytime I need to debug through the JDK source code it is incorrect - IDEA uses the source code attached to the app's module, which is out of sync (JDK1.4.2) with the JRE used to run the app (JDK1.5). The option should be "Use alternative JDK" and give the user the option to select one of the JDKs configured in IDEA - then you could use one with the correct source attached to it.