Ubuntu Multimedia :: Webcam - Uvcvideo: Failed To Resubmit Video URB (-27)

I have a Dell 1300 running Kubuntu 11 and attached is a Logitech Pro 9000 webcam. It works OK - in the sense that Cheese, VLC etc display correctly. I'm trying to set up video streaming for security monitoring - and because the Dell is pretty slow, I need to stream at a low rate of frames/sec to keep a reasonably low cpu utilisation. I've tried various things, but the most successful is the motion package, which I can set up with a new frame each second, which is fine. However, the motion server stops after a seemingly random period with the message ...

[0] Thread 1 - Watchdog timeout, trying to do a graceful restart
[0] httpd - Finishing
[0] httpd Closing
[0] httpd thread exit
[0] Thread 1 - Watchdog timeout, did NOT restart graceful,killing it!
[0] Calling vid_close() from motion_cleanup
[0] Closing video device /dev/video0

Motion hasn't crashed, it's still running. I also get a message in syslog ... uvcvideo: Failed to resubmit video URB (-27)