[ptx] error using autopano-sift

[Paradoxa]

Unhandled Exception: System.Exception: BUG: less than three neighbours!
in <0x0036f> MultiMatch:BuildGlobalMatchList ()
in <0x000f2> MultiMatch:TwoPatchMatch
(System.Collections.ArrayList,int,int,System.Collections.ArrayList,int,int,bool)
in <0x00836> Autopano:RefineKeypoints
(System.Collections.ArrayList,bool,bool)
in <0x008c8> Autopanog:OnComputeClicked (object,System.EventArgs)
in <0x00069> (wrapper delegate-invoke)
System.MulticastDelegate:invoke_void_object_EventArgs
(object,System.EventArgs)
in <0x0012d> GtkSharp.voidObjectSignal:voidObjectCallback (intptr,int)
in <0x0005a> (wrapper native-to-managed)
GtkSharp.voidObjectSignal:voidObjectCallback (intptr,int)
in (unmanaged) (wrapper managed-to-native) Gtk.Application:gtk_main ()
in <0x00004> (wrapper managed-to-native) Gtk.Application:gtk_main ()
in <0x00007> Gtk.Application:Run ()
in <0x00339> Autopanog:Main (string[])

some explication???
for me means nothing... :-)