After setting up a new Eclipse instance, checking out my current GWT project it’s time for a first test, so I fire up the DevMode and: NullPointerException at SwingUI(42)
That particular class is part of the GWT DevMode and tries to load an image from the class path by requesting it from SwingUI’s class loader which turns out to be null. The reason is that by mistake I added all GWT jars to the bootstrap classpath of the launch configuration, just moving them to the “User Entries” section fixes the problem.
George's Techblog 