Thanks, but I couldn't see the relevance of those links.

But I was running it in full speed mode since I couldn't get it working in high speed mode, and even plugged into my netbook it seems to connect to the USB sound card in full speed mode, however I tried it on my other N900 and that did connect in high speed mode. And I did get it working again for a while on that N900 with pulseaudio, however when I switched pulseaudio back to internal speakers and then tried to switch back to the USB soundcard again, it locked up requiring me to unplug the USB soundcard to get my N900 responding again, and it resulted in another lot of messages in dmesg which were similar, but not identical.