I have the silent hanging problem in Ubuntu 13.10, with 2 different sound sources.
Actually, it doesn't hang: it continues to work and record things (both audio and video). The problem is the window disappears and you cannot stop it. Key shortcuts (found on http://www.webupd8.org/2012/10/kazam-screencaster-132-gets-new-ui.html) do not work either.
If you kill the process by hand (killall -9 kazam), the videos are available wherever you configured them to be in "Preferences" with a ".movie" extension, but as you selected the format, you can quite easily rename them to ".webm" for example and have your video, but apparently the movie index is not correct, so you don't have a clear "total time" for the video (so not perfect, although it can probably be fixed by mplayer, ffmpeg or something like that).

This is really annoying. Kazam was the most reliable desktop recording tool I had found for Ubuntu.

When launching with --debug, I get the following output.

$ kazam --debug
DEBUG Kazam - Starting ...
DEBUG Kazam - Running on: Ubuntu 13.10
DEBUG Kazam - Kazam version: 1.4.3-0ubuntu1 NCC-2000
DEBUG Kazam - Starting new instance ...
DEBUG Constants - Getting hardware specs
DEBUG Constants - Getting Video sources.
DEBUG Constants - Found 3 monitor(s).
DEBUG Constants -   Monitor 0 - X: 0, Y: 0, W: 1920, H: 1080
DEBUG Constants -   Monitor 1 - X: 1920, Y: 0, W: 1920, H: 1080
DEBUG Constants -   Monitor 2 - X: 3840, Y: 0, W: 1680, H: 1050
DEBUG Constants -   Combined screen - X: 0, Y: 0, W: 5520, H: 1080
DEBUG Prefs - XDG_PICTURES is a directory and accessible
DEBUG Main - Gstreamer version detected: 1.2.0.0
DEBUG Main - Setting variables.
DEBUG PulseAudio - Starting mainloop.
DEBUG PulseAudio - Getting API.
DEBUG PulseAudio - Setting context.
DEBUG PulseAudio - Set state callback.
DEBUG PulseAudio - Connecting to server.
DEBUG PulseAudio - Start mainloop.
DEBUG PulseAudio - State connected.
DEBUG Main - Connecting indicator signals.
DEBUG Main - Starting in silent mode: False
DEBUG Indicator - Indicatior silent: False
DEBUG Indicator - Trying to bind hotkeys.
DEBUG Main - Main Window UI setup.
DEBUG Main - Unable to get name for '<Adjustment object at 0x7f4f6c1bd050 (GtkAdjustment at 0x24d59c0)>'

(kazam:1079): Gtk-WARNING **: Can't set a parent on widget which has a parent


(kazam:1079): Gtk-WARNING **: Can't set a parent on widget which has a parent

DEBUG Prefs - Getting Audio sources.
DEBUG PulseAudio - get_audio_sources() called.
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 0
DEBUG PulseAudio -   Name: b'alsa_output.pci-0000_00_1b.0.analog-stereo.monitor'
DEBUG PulseAudio -   Desc: b'Monitor of Audio interne St\xc3\xa9r\xc3\xa9o analogique'
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 1
DEBUG PulseAudio -   Name: b'alsa_input.pci-0000_00_1b.0.analog-stereo'
DEBUG PulseAudio -   Desc: b'Audio interne St\xc3\xa9r\xc3\xa9o analogique'
DEBUG PulseAudio - pa_sourcelist_cb()
DEBUG PulseAudio -   IDX: 4
DEBUG PulseAudio -   Name: b'alsa_input.usb-BEHRINGER_C-1U-00-C1U.analog-stereo'
DEBUG PulseAudio -   Desc: b'C-1U                      St\xc3\xa9r\xc3\xa9o analogique'
DEBUG PulseAudio - pa_sourcelist_cb() -- finished
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 0
DEBUG Prefs -   - alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG Prefs -   - Monitor of Audio interne Stéréo analogique
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 1
DEBUG Prefs -   - alsa_input.pci-0000_00_1b.0.analog-stereo
DEBUG Prefs -   - Audio interne Stéréo analogique
DEBUG Prefs -  Device found: 
DEBUG Prefs -   - 4
DEBUG Prefs -   - alsa_input.usb-BEHRINGER_C-1U-00-C1U.analog-stereo
DEBUG Prefs -   - C-1U Stéréo analogique
DEBUG Main - Capture cursor: True.
DEBUG Main - Capture speakers: True.
DEBUG Main - Capture cursor_pic: True.
DEBUG Main - Capture borders_pic: True.
DEBUG Main - Start delay now: 3
DEBUG Main - Area ON.
DEBUG Window Select - Initializing select window.
DEBUG Window Select - Compositing window manager detected.
DEBUG Main - Area mode clicked.
DEBUG Window Select - Move to X: 3840 Y: 0
DEBUG Window Select - Selected coords: 4024 292 4651 912
DEBUG Main - Area selected: SX: 184, SY: 292, EX: 811, EY: 912
DEBUG Main - Area selected: GX: 4024, GY: 292, GX: 4651, GY: 912
DEBUG Window Select - Move to X: 3840 Y: 0
DEBUG Main - Record clicked, invoking Screencast.
DEBUG GStreamer - Audio_source : alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG GStreamer - Audio2_source : None
DEBUG GStreamer - Video_source: {'x': 1920, 'y': 0, 'width': 1920, 'height': 1080}
DEBUG GStreamer - Xid: None
DEBUG GStreamer - Area: (4024, 292, 4651, 912, 627, 620)
DEBUG GStreamer - Capture Cursor: True
DEBUG GStreamer - Framerate : 25.0
DEBUG GStreamer - Capturing area.
DEBUG GStreamer - Coordinates SX: 4024 SY: 292 EX: 4651 EY: 912
DEBUG GStreamer - testing for xid: None
DEBUG GStreamer - Codec: VP8 / WEBM
DEBUG GStreamer - Setup audio elements.
DEBUG GStreamer - Audio1 Source:
  alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
DEBUG GStreamer - Filesink: /home/ywarnier/Vidéos/kazam_njcbv8.movie
DEBUG GStreamer - Linking Video
DEBUG GStreamer - Linking Audio
DEBUG GStreamer -  Link audiosrc -> aud_in_queue: True
DEBUG GStreamer -  Link aud_in_queue -> aud_caps_filter: True
DEBUG GStreamer -  Link aud_caps_filter -> audioconv: True
DEBUG GStreamer - Link audioconv -> audioenc: True
DEBUG GStreamer - Link audioenc -> aud_out_queue: True
DEBUG GStreamer - Link aud_out_queue -> mux: True
DEBUG GStreamer - Link mux -> file queue: True
DEBUG GStreamer - Link file queue -> sink: True
DEBUG Main - Hiding main window.
DEBUG Main - Showing recording outline.
DEBUG Outline Window - Initializing outline window.
DEBUG Outline Window - Compositing window manager detected.
DEBUG Outline Window - Trying to determine Unity Launcher and Panel sizes.
DEBUG Main - Counter finished.
DEBUG Indicator - Recording started.
DEBUG GStreamer - Setting STATE_PLAYING