Run:

---%<---
import javax.swing.JComponent;
import javax.swing.UIManager;
import javax.swing.plaf.ComponentUI;
public class UIDefaults_getError {
    public static void main(String[] x) {
        JComponent c = new JComponent() {
            @Override
            public String getUIClassID() {
                return "fake";
            }
            @Override
            public String toString() {
                return "<the component>";
            }
        };
        UIManager.getDefaults().put("fake", FakeID.class.getName());
        UIManager.getDefaults().getUI(c);
    }
    public static class FakeID extends ComponentUI {
        public static FakeID createUI(JComponent c) {
            throw new IllegalStateException("Oops!");
        }
    }
}
---%<---

I get:

---%<---
java version "1.7.0-ea"
Java(TM) SE Runtime Environment (build 1.7.0-ea-b04)
Java HotSpot(TM) Client VM (build 1.7.0-ea-b04, mixed mode, sharing)

UIDefaults.getUI() failed: createUI() failed for <the component> java.lang.reflect.InvocationTargetException
java.lang.Error
        at javax.swing.UIDefaults.getUIError(UIDefaults.java:706)
        at javax.swing.MultiUIDefaults.getUIError(MultiUIDefaults.java:117)
        at javax.swing.UIDefaults.getUI(UIDefaults.java:752)
        at UIDefaults_getError.main(UIDefaults_getError.java:17)
---%<---

Note that the original stack trace is lost; even its message is gone.