[LAU] No sound from Presonus FP10

Hi. I'm in the process of setting up a 64 bit Archlinux system and I'm stumped by a problem with playback on my FP10. * I can start jackd. * The light on the FP10 turns blue. * In qjackctl I can see programs (mplayer, ardour, etc.) making connections to the default output pair. * I can record in ardour and hear analog inputs being played back through the monitors. Everything seems perfect aside from not beight able to get any sound from the PC ;-( Has anyone else experienced this kind of thing? Have I missed something obvious? I would really appreciate some help at this point. FFADO version is 1.999.41-1518 jack is jackdmp 1.90 Regards, Jesse