[LAU] Zoom H4n as interface / no duplex

Hello, I have a Zoom H4n recorder and would like to use it as an interface on a laptop with Ubuntu 10.04.. I've succeeded in using it to record and to play audio independently via jack but not together in duplex mode. I've read on the web that people have used the H4n with full duplex. Can anyone suggest what might be wrong with my set up? No problems using the built-in sound card of the laptop in duplex mode with jack. I'll paste below the verbose messages from qjackctl. Cheers, Iain 07:23:26.322 Patchbay activated. 07:23:26.334 Statistics reset. 07:23:26.339 ALSA connection change. 07:23:26.356 Startup script... 07:23:26.357 artsshell -q terminate 07:23:26.402 ALSA connection graph change. sh: artsshell: not found 07:23:26.829 Startup script terminated with exit status=32512. 07:23:26.830 JACK is starting... 07:23:26.830 /usr/bin/jackd -v -dalsa -dhw:1 -r48000 -p256 -n3 -Xseq jackd 0.118.0 Copyright 2001-2009 Paul Davis, Stephane Letz, Jack O'Quinn, Torben Hohn and others. jackd comes with ABSOLUTELY NO WARRANTY This is free software, and you are welcome to redistribute it under certain conditions; see the file COPYING for details getting driver descriptor from /usr/lib/jack/jack_oss.so getting driver descriptor from /usr/lib/jack/jack_net.so getting driver descriptor from /usr/lib/jack/jack_dummy.so getting driver descriptor from /usr/lib/jack/jack_alsa.so getting driver descriptor from /usr/lib/jack/jack_firewire.so 07:23:26.845 JACK was started with PID=5059. no message buffer overruns JACK compiled with System V SHM support. server `default' registered loading driver .. registered builtin port type 32 bit float mono audio registered builtin port type 8 bit raw midi clock source = system clock via clock_gettime new client: alsa_pcm, id = 1 type 1 @ 0x84ea9c8 fd = -1 apparent rate = 48000 creating alsa driver ... hw:1|hw:1|256|3|48000|0|0|nomon|swmeter|-|32bit control device hw:1 configuring for 48000Hz, period = 256 frames (5.3 ms), buffer = 3 periods ALSA: final selected sample format for capture: 16bit little-endian ALSA: use 3 periods for capture start poll on 3 fd's ALSA: final selected sample format for playback: 16bit little-endian ALSA: use 3 periods for playback new buffer size 256 registered port system:capture_1, offset = 1024 registered port system:capture_2, offset = 2048 registered port system:playback_1, offset = 0 registered port system:playback_2, offset = 0 ++ jack_sort_graph ++ jack_rechain_graph(): +++ client is now alsa_pcm active ? 1 client alsa_pcm: internal client, execution_order=0. -- jack_rechain_graph() -- jack_sort_graph registered port alsa_pcm:Midi-Through/midi_capture_1, offset = 1024 registered port alsa_pcm:Midi-Through/midi_playback_1, offset = 0 ALSA: could not start playback (Broken pipe) DRIVER NT: could not start driver cannot start driver starting server engine shutdown server thread back from poll stopping driver unloading driver freeing shared port segments stopping server thread stopping watchdog thread last xrun delay: 0.000 usecs max delay reported by backend: 0.000 usecs freeing engine shared memory max usecs: 0.000, engine deleted cleaning up shared memory cleaning up files unregistering server `default' 07:23:26.937 JACK was stopped successfully. 07:23:26.939 Post-shutdown script... 07:23:26.940 killall jackd 07:23:27.032 ALSA active patchbay scan... jackd: no process found 07:23:27.354 Post-shutdown script terminated with exit status=256. 07:23:29.044 Could not connect to JACK server as client. - Overall operation failed. - Unable to connect to server. Please check the messages window for more info.