The Eclipse Scala plugin enters comatose state (as described in bug #437) when using a version of Scala that has\
 run-time types enabled.

This is the (lovely) error message that brings the comatose state about:
An error occured while automatically activating bundle ch.epfl.lamp.sdt.ui (89).
at org.eclipse.ui.internal.Workbench$14.run(Workbench.java:1260)
at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1029)
at org.eclipse.core.runtime.Platform.run(Platform.java:775)
at org.eclipse.ui.internal.Workbench.restoreState(Workbench.java:1204)
at org.eclipse.ui.internal.WorkbenchConfigurer.restoreState(WorkbenchConfigurer.java:173)
at org.eclipse.ui.application.WorkbenchAdvisor.openWindows(WorkbenchAdvisor.java:700)
at org.eclipse.ui.internal.Workbench.init(Workbench.java:981)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1541)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:315)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:143)
at org.eclipse.ui.internal.ide.IDEApplication.run(IDEApplication.java:103)
at org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:230)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:371)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:160)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.eclipse.core.launcher.Main.invokeFramework(Main.java:330)
at org.eclipse.core.launcher.Main.basicRun(Main.java:274)
at org.eclipse.core.launcher.Main.run(Main.java:977)
at org.eclipse.core.launcher.Main.main(Main.java:952)
Caused by: java.lang.reflect.InvocationTargetException
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:327)
at org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:447)
at org.eclipse.ui.internal.progress.ProgressMonitorJobsDialog.run(ProgressMonitorJobsDialog.java:261)
at org.eclipse.ui.internal.progress.ProgressManager$3.run(ProgressManager.java:861)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:69)
at org.eclipse.ui.internal.progress.ProgressManager.busyCursorWhile(ProgressManager.java:895)
at org.eclipse.ui.internal.progress.ProgressManager.busyCursorWhile(ProgressManager.java:871)
at ch.epfl.lamp.sdt.ui.ScalaUIPlugin.start(ScalaUIPlugin.java:66)
at org.eclipse.osgi.framework.internal.core.BundleContextImpl$2.run(BundleContextImpl.java:994)
at java.security.AccessController.doPrivileged(Native Method)
at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:988)
... 56 more
Caused by: java.lang.Error: java.lang.ClassNotFoundException: scala.tools.scalac.ast.printer.TextTreePrinter$Tex\
t
at scala.runtime.types.TypeConstructor.(TypeConstructor.java:106)
at scala.tools.scalac.ast.printer.TextTreePrinter$class.(TextTreePrinter.scala:90)
at scala.tools.scalac.Global$class.newTextTreePrinter(Global.scala:36)
at scalac.Global.(Global.java:273)
at scala.tools.scalac.Global$class.(Global.scala:27)
at scala.tools.scalac.Global$class.(Global.scala:30)
at scala.tools.scalac.Global$class.(Global.scala:31)
at ch.epfl.lamp.sdt.compatibility.scalac.SDTScalacAdapter.createGlobal(Unknown Source)
at ch.epfl.lamp.sdt.compatibility.scalac.SDTScalacAdapter.compile(Unknown Source)
at ch.epfl.lamp.sdt.core.build.ScalaProjectBuilder.build(ScalaProjectBuilder.java:63)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:585)
at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1029)
at org.eclipse.core.runtime.Platform.run(Platform.java:775)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:168)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:202)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:231)
at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1029)
at org.eclipse.core.runtime.Platform.run(Platform.java:775)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:234)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:253)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:282)
at org.eclipse.core.internal.resources.Workspace.build(Workspace.java:211)
at ch.epfl.lamp.sdt.ui.ScalaUIPlugin$1.run(ScalaUIPlugin.java:69)
at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:113)
Caused by: java.lang.ClassNotFoundException: scala.tools.scalac.ast.printer.TextTreePrinter$Text
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:242)
at scala.runtime.types.TypeConstructor.(TypeConstructor.java:104)
... 23 more
Root exception:
java.lang.Error: java.lang.ClassNotFoundException: scala.tools.scalac.ast.printer.TextTreePrinter$Text
at scala.runtime.types.TypeConstructor.(TypeConstructor.java:106)
at scala.tools.scalac.ast.printer.TextTreePrinter$class.(TextTreePrinter.scala:90)
at scala.tools.scalac.Global$class.newTextTreePrinter(Global.scala:36)
at scalac.Global.(Global.java:273)
at scala.tools.scalac.Global$class.(Global.scala:27)
at scala.tools.scalac.Global$class.(Global.scala:30)
at scala.tools.scalac.Global$class.(Global.scala:31)
at ch.epfl.lamp.sdt.compatibility.scalac.SDTScalacAdapter.createGlobal(Unknown Source)
at ch.epfl.lamp.sdt.compatibility.scalac.SDTScalacAdapter.compile(Unknown Source)
at ch.epfl.lamp.sdt.core.build.ScalaProjectBuilder.build(ScalaProjectBuilder.java:63)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:585)
at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1029)
at org.eclipse.core.runtime.Platform.run(Platform.java:775)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:168)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:202)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:231)
at org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1029)
at org.eclipse.core.runtime.Platform.run(Platform.java:775)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:234)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:253)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:282)
at org.eclipse.core.internal.resources.Workspace.build(Workspace.java:211)
at ch.epfl.lamp.sdt.ui.ScalaUIPlugin$1.run(ScalaUIPlugin.java:69)
at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:113)
Caused by: java.lang.ClassNotFoundException: scala.tools.scalac.ast.printer.TextTreePrinter$Text
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forNameAn error occured while automatically activating bundle ch.epfl.lamp.sdt.ui (89).(Class\
.java:242)
at scala.runtime.types.TypeConstructor.(TypeConstructor.java:104)
... 23 more