Spoke too soon:

(/usr/lib/banshee-1/Banshee.exe:6028): Gtk-CRITICAL **: gtk_action_group_get_action: assertion `GTK_IS_ACTION_GROUP (action_group)' failed
Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.NullReferenceException: Object reference not set to an instance of an object
  at Banshee.Lastfm.Radio.LastfmActions.UpdateActions () [0x00000] 
  at Banshee.Lastfm.Radio.LastfmActions.OnPlaybackSourceChanged (System.Object o, System.EventArgs args) [0x00000] 
  at (wrapper delegate-invoke) System.EventHandler:invoke_void__this___object_EventArgs (object,System.EventArgs)
  at Banshee.PlaybackController.PlaybackControllerService.OnSourceChanged () [0x00000] 
  at Banshee.PlaybackController.PlaybackControllerService.set_Source (ITrackModelSource value) [0x00000] 
  at Banshee.PlaybackController.PlaybackControllerService.set_NextSource (ITrackModelSource value) [0x00000] 
  at Banshee.PlaybackController.PlaybackControllerService.set_Source (ITrackModelSource value) [0x00000] 
  at Banshee.PlaybackController.PlaybackControllerService.<PlaybackControllerService>m__20 (Banshee.Sources.SourceEventArgs ) [0x00000] 
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at (wrapper delegate-invoke) Banshee.Sources.SourceEventHandler:invoke_void__this___SourceEventArgs (Banshee.Sources.SourceEventArgs)
  at Banshee.Sources.SourceManager.SetActiveSource (Banshee.Sources.Source source, Boolean notify) [0x00000] 
  at Banshee.Sources.SourceManager.SetActiveSource (Banshee.Sources.Source source) [0x00000] 
  at Banshee.Sources.Gui.SourceView.OnButtonPressEvent (Gdk.EventButton press) [0x00000] 
  at Gtk.Widget.buttonpressevent_cb (IntPtr widget, IntPtr evnt) [0x00000] 
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at Gtk.Widget.buttonpressevent_cb(IntPtr widget, IntPtr evnt)
   at Gtk.Application.gtk_main()
   at Gtk.Application.Run()
   at Banshee.Gui.GtkBaseClient.Run()
   at Banshee.Gui.GtkBaseClient.Startup()
   at Hyena.Gui.CleanRoomStartup.Startup(Hyena.Gui.StartupInvocationHandler startup)
   at Banshee.Gui.GtkBaseClient.Startup()
   at Banshee.Gui.GtkBaseClient.Startup(System.String[] args)
   at Nereid.Client.Main(System.String[] args)
   at System.AppDomain.ExecuteAssembly(System.Reflection.Assembly , System.String[] )
   at System.AppDomain.ExecuteAssemblyInternal(System.Reflection.Assembly a, System.String[] args)
   at System.AppDomain.ExecuteAssembly(System.String assemblyFile, System.Security.Policy.Evidence assemblySecurity, System.String[] args)
   at System.AppDomain.ExecuteAssembly(System.String assemblyFile)
   at Booter.Booter.BootClient(System.String clientName)
   at Booter.Booter.Main()