I get the following error when attempting to configure a JBoss 3.2.x server under Eclipse 3.2M5 + JBoss 1.5.1GA: Any ideas why?

java.lang.NoClassDefFoundError: org/eclipse/jdt/internal/debug/ui/launcher/JavaLaunchConfigurationTab
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.defineClass(DefaultClassLoader.java:158)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClass(ClasspathManager.java:491)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findClassImpl(ClasspathManager.java:461)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClassImpl(ClasspathManager.java:420)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:403)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:186)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findLocalClass(BundleLoader.java:338)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:390)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:351)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:81)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at org.jboss.ide.eclipse.launcher.ui.configuration.jboss.JBoss32xTabGroup.createTabs(JBoss32xTabGroup.java:44)
at org.eclipse.debug.internal.ui.launchConfigurations.CreateLaunchConfigurationAction.performAction(CreateLaunchConfigurationAction.java:70)
at org.eclipse.debug.internal.ui.launchConfigurations.AbstractLaunchConfigurationAction$1.run(AbstractLaunchConfigurationAction.java:103)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:69)
at org.eclipse.debug.internal.ui.launchConfigurations.AbstractLaunchConfigurationAction.run(AbstractLaunchConfigurationAction.java:106)
at org.eclipse.ui.actions.BaseSelectionListenerAction.runWithEvent(BaseSelectionListenerAction.java:167)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:530)
at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:480)
at org.eclipse.jface.action.ActionContributionItem$6.handleEvent(ActionContributionItem.java:433)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:66)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:925)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3287)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2907)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:811)
at org.eclipse.jface.window.Window.open(Window.java:789)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationsDialog.open(LaunchConfigurationsDialog.java:1321)
at org.eclipse.debug.ui.DebugUITools$1.run(DebugUITools.java:375)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:69)
at org.eclipse.debug.ui.DebugUITools.openLaunchConfigurationDialogOnGroup(DebugUITools.java:379)
at org.eclipse.debug.ui.DebugUITools.openLaunchConfigurationDialogOnGroup(DebugUITools.java:321)
at org.eclipse.debug.ui.actions.OpenLaunchDialogAction.run(OpenLaunchDialogAction.java:80)
at org.eclipse.jface.action.Action.runWithEvent(Action.java:492)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:530)
at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:480)
at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:392)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:66)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:925)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3287)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2907)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:1899)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1863)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:417)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:143)
at org.eclipse.ui.internal.ide.IDEApplication.run(IDEApplication.java:106)
at org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:99)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:92)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:68)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:374)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:169)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.core.launcher.Main.invokeFramework(Main.java:338)
at org.eclipse.core.launcher.Main.basicRun(Main.java:282)
at org.eclipse.core.launcher.Main.run(Main.java:977)
at org.eclipse.core.launcher.Main.main(Main.java:952)