Originally reported at:
  https://bugs.launchpad.net/bugs/885693

Start Banshee, click on Amazon MP3 Store in the menu on the left. Banshee freezes.

Oneiric AMD64

Here is the output of the console:

:~$ banshee 
[Info  14:50:48.359] Running Banshee 2.2.0: [Ubuntu 11.10 (linux-gnu, x86_64) @ 2011-10-31 19:36:13 UTC]
[Info  14:50:49.058] Updating web proxy from GConf
[Info  14:50:49.164] All services are started 0,654819
[Info  14:50:49.719] AmazonMP3 store redirect URL: https://one.ubuntu.com/music/store/amz/
** (Banshee:2528): DEBUG: SyncDaemon already running, initializing SyncdaemonDaemon object

(Banshee:2528): libsoup-WARNING **: No feature manager for feature of type 'U1RequestChrome'

(Banshee:2528): Gtk-CRITICAL **: IA__gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed
** (Banshee:2528): DEBUG: Loading the real store page
[Info  14:50:51.367] nereid Client Started
[Info  14:50:51.420] GStreamer version 0.10.35.0, gapless: True, replaygain: False
[Info  14:50:51.654] AppleDeviceSource is ignoring unmounted volume 11 GB-Dateisystem

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.WebSource.WebSource.Activate () [0x00000] in <filename unknown>:0 
  at Banshee.Sources.SourceManager.SetActiveSource (Banshee.Sources.Source source, Boolean notify) [0x00000] in <filename unknown>:0 
  at Banshee.Sources.SourceManager.SetActiveSource (Banshee.Sources.Source source) [0x00000] in <filename unknown>:0 
  at Banshee.Sources.Gui.SourceView.OnButtonPressEvent (Gdk.EventButton press) [0x00000] in <filename unknown>:0 
  at Gtk.Widget.buttonpressevent_cb (IntPtr widget, IntPtr evnt) [0x00000] in <filename unknown>:0 
   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.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()