Leaves application responsive but UI will not open. Trace as follows.

Running Banshee 2.2.0: [Ubuntu oneiric (development branch) (linux-gnu, x86_64) @ 2011-09-23 04:47:58 UTC]

Marshaling size_request signal
Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> GLib.GException: Configuration server couldn't be contacted: D-BUS error: Method "Set" with signature "s(ii)" on interface "org.gnome.GConf.Database" doesn't exist

  at GConf.Client.SetValue (System.String key, GConf.Value val) [0x00000] in <filename unknown>:0 
  at GConf.ClientBase.Set (System.String key, System.Object val) [0x00000] in <filename unknown>:0 
  at Banshee.GnomeBackend.GConfConfigurationClient.Set[Int32] (System.String namespace, System.String key, Int32 value) [0x00000] in <filename unknown>:0 
  at Banshee.Configuration.ConfigurationClient.Set[Int32] (System.String namespace, System.String key, Int32 value) [0x00000] in <filename unknown>:0 
  at Banshee.Configuration.ConfigurationClient.Set[Int32] (SchemaEntry`1 entry, Int32 value) [0x00000] in <filename unknown>:0 
  at Banshee.Configuration.SchemaEntry`1[System.Int32].Set (Int32 value) [0x00000] in <filename unknown>:0 
  at Nereid.PlayerInterface.<ConnectEvents>m__5 (System.Object , Gtk.SizeRequestedArgs ) [0x00000] in <filename unknown>:0 
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0 
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0 
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0 
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <filename unknown>:0 
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0 
  at GLib.SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0 
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000] in <filename unknown>:0 
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)
   at Gtk.Widget.gtksharp_widget_base_show(IntPtr )
   at Gtk.Widget.OnShown()
   at Nereid.PlayerInterface.OnShown()
   at Gtk.Widget.shown_cb(IntPtr widget)
   at Gtk.Window.gtk_window_present(IntPtr )
   at Gtk.Window.Present()
   at Banshee.Gui.BaseClientWindow.SetVisible(Boolean visible)
   at Banshee.Mpris.MediaPlayer.Raise()
   at DBus.MessageReader.Caller(System.Object , DBus.MessageReader , DBus.Message , DBus.MessageWriter )
   at DBus.ExportObject.HandleMethodCall(DBus.MethodCall method_call)
   at DBus.Connection.HandleMethodCall(DBus.MethodCall method_call)
   at DBus.Connection.HandleMessage(DBus.Message msg)
   at DBus.Connection.Iterate()
   at DBus.BusG+<Init>c__AnonStorey0.<>m__0(IntPtr source, IOCondition condition, IntPtr data)
   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.AppDomain , 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()
^C