Steps to reproduce:
1. Select "Import Folder" from the File menu
2. Select a folder
3. Click "Import"


Stack trace:
Unhandled Exception: Glade.HandlerNotFoundException: No handler OnWindowResponse found for signal response
at SignalConnector.ConnectFunc (intptr,intptr,intptr,intptr,intptr,int,intptr) <0x00301>
at (wrapper native-to-managed) SignalConnector.ConnectFunc (intptr,intptr,intptr,intptr,intptr,int,intptr) <0x0004b>
in (unmanaged) 0xb63ac81a
at (wrapper managed-to-native) SignalConnector.glade_xml_signal_autoconnect_full (intptr,Glade.XML/SignalConnector/RawXMLConnectFunc,intptr) <0x00004>
at SignalConnector.Autoconnect () <0x00059>
at Glade.XML.Autoconnect (object) <0x00042>
at Muine.ProgressWindow..ctor (Gtk.Window) <0x00043>
at AddFoldersThread..ctor (System.Collections.ArrayList) <0x0006c>
at Muine.SongDatabase.AddWatchedFolders (System.Collections.ArrayList) <0x001db>
at Muine.ImportDialog.OnResponse (object,Gtk.ResponseArgs) <0x00162>
at (wrapper delegate-invoke) System.MulticastDelegate.invoke_void_object_ResponseArgs (object,Gtk.ResponseArgs) <0x00041>
at Gtk.Dialog.ResponseSignalCallback (intptr,int,intptr) <0x000ff>
at (wrapper native-to-managed) Gtk.Dialog.ResponseSignalCallback (intptr,int,intptr) <0x00038>
in (unmanaged) 0xb6b8ecb3
at (wrapper managed-to-native) Gtk.Application.gtk_main () <0x00004>
at Gtk.Application.Run () <0x00007>
at Muine.Global.Main (string[]) <0x00573>

Other information:
I'm using the latest mono (1.1.17.1) and have seen many applications crash like this with it. So it might have to do with adjusting the handlers' arguments.