Here is a patch for /usr/src/linux-2.6.3/drivers/bluetooth/hci_usb.c

Without the interval set, the latest kernel 2.6.3 usb code will reject 
the usb_submit_urb().

Without this patch no ISOC urbs are submitted, and thus no SCO data is 
passed.

The proper fix would really be to only enable these when a SCO 
connection is actually open.

Cheers
James