Xact and Yealink

I tried out the YeaPhone software, running on SlugOS/BE v4.8 on an NSLU2, to connect to a XACT XVP620 phone. Because the repository already had linphonec and yealink available, I avoided having to build them from scratch (I'm stating this as it may be a source of the following problem). Following the configuration guide on the YeaPhone site, I was able to cause linphonec to initiate calls and use the handset (hear/speak). However, there was a lot of annoying clicking in the call and the calls tended to fail after a couple minutes.

Below is a capture from dmesg on the NSLU2.

input: Yealink usb-p1k as /class/input/input1
usbcore: registered new interface driver yealink
drivers/usb/input/yealink.c: Yealink phone driver:yld-20051230
usbcore: registered new interface driver snd-usb-audio
drivers/usb/input/yealink.c: urb_irq_callback - urb status -2
drivers/usb/input/yealink.c: urb_ctl_callback - usb_submit_urb failed -1
drivers/usb/input/yealink.c: urb_ctl_callback - urb status -2
drivers/usb/input/yealink.c: urb_irq_callback - urb status -2
drivers/usb/input/yealink.c: urb_ctl_callback - usb_submit_urb failed -1
drivers/usb/input/yealink.c: urb_irq_callback - urb status -2
drivers/usb/input/yealink.c: urb_ctl_callback - usb_submit_urb failed -1
drivers/usb/input/yealink.c: urb_ctl_callback - urb status -2
drivers/usb/input/yealink.c: urb_irq_callback - urb status -2
drivers/usb/input/yealink.c: unexpected response 11
drivers/usb/input/yealink.c: urb_irq_callback - urb status -2
drivers/usb/input/yealink.c: unexpected response 2
drivers/usb/input/yealink.c: unexpected response 4
drivers/usb/input/yealink.c: urb_irq_callback - usb_submit_urb failed -22