Some strange behavior I saw in 977 project configuration:
I had one module with one content. Removed the module itself, added the a new module with content. Forgot to set the JDK. Compile failed since no JDK specified. Specified the JDK in the project configuration for the module, apply, still compilation does not go through with the no jdk specified error.
Another interesting thing is when this dialog box comes up and you click OK, it brings up the project properties dialog, but the module configuration and JDK configuration has moved to the new window.