This is the trace:

[1 Warn  17:16:25.879] Caught an exception - System.NullReferenceException: Object reference not set to an instance of an object (in `f-spot')
  at FSpot.Loaders.ImageLoader.Create (Hyena.SafeUri uri) [0x00007] in /usr/src/f-spot/src/Loaders/ImageLoader.cs:45 
  at FSpot.Widgets.PhotoImageView.Load (Hyena.SafeUri uri) [0x00021] in /usr/src/f-spot/src/PhotoImageView.cs:180 
  at FSpot.Widgets.PhotoImageView.HandlePhotoItemChanged (System.Object sender, FSpot.BrowsablePointerChangedEventArgs args) [0x0012b] in /usr/src/f-spot/src/PhotoImageView.cs:317 
[4 Debug 17:16:25.880] Invalid thumbnail, reloading: gphoto2://[usb:002,007]/DCIM/100NCD90/DSC_6278.JPG
Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
GLib.GException: Operation not supported by backend
  at GLib.FileInputStream.QueryInfo (System.String attributes, GLib.Cancellable cancellable) [0x00000] 
  at GLib.GioStream.get_Length () [0x00000] 
  at TagLib.File.get_Length () [0x00000] in /usr/src/f-spot/lib/TagLib/TagLib/src/TagLib/File.cs:379 
  at TagLib.Jpeg.File.ReadSegmentSize () [0x0004a] in /usr/src/f-spot/lib/TagLib/TagLib/src/TagLib/Jpeg/File.cs:331 
  at TagLib.Jpeg.File.ReadMetadata () [0x00029] in /usr/src/f-spot/lib/TagLib/TagLib/src/TagLib/Jpeg/File.cs:355 
  at TagLib.Jpeg.File.Read (ReadStyle propertiesStyle) [0x0001d] in /usr/src/f-spot/lib/TagLib/TagLib/src/TagLib/Jpeg/File.cs:246 
  at TagLib.Jpeg.File..ctor (IFileAbstraction abstraction, ReadStyle propertiesStyle) [0x00007] in /usr/src/f-spot/lib/TagLib/TagLib/src/TagLib/Jpeg/File.cs:167 
  at (wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke (object,object[],System.Exception&)
  at System.Reflection.MonoCMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] 
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at Gtk.Widget.exposeevent_cb(IntPtr widget, IntPtr evnt)
   at Gdk.Window.gdk_window_process_updates(IntPtr , Boolean )
   at Gdk.Window.ProcessUpdates(Boolean update_children)
   at FSpot.Widgets.IconView.SetSize(Int32 x, Int32 y, Int32 width, Int32 height) in /usr/src/f-spot/src/Widgets/IconView.cs:line 816
   at FSpot.Widgets.IconView.UpdateLayout(Rectangle allocation) in /usr/src/f-spot/src/Widgets/IconView.cs:line 776
   at FSpot.Widgets.IconView.OnSizeAllocated(Rectangle allocation) in /usr/src/f-spot/src/Widgets/IconView.cs:line 1483
   at Gtk.Widget.sizeallocated_cb(IntPtr widget, IntPtr allocation)
   at Gtk.Application.gtk_main()
   at Gtk.Application.Run()
   at FSpot.Driver.Startup() in /usr/src/f-spot/src/main.cs:line 328
   at Hyena.Gui.CleanRoomStartup.Startup(Hyena.Gui.StartupInvocationHandler startup) in /usr/src/f-spot/lib/Hyena/Hyena.Gui/Hyena.Gui/CleanRoomStartup.cs:line 54
   at FSpot.Driver.Main(System.String[] args) in /usr/src/f-spot/src/main.cs:line 272