Comment 4 for bug 459523

details of the working system:

it's the same hardware, with an earlier version of ubuntu installed on a separate hard disk.
$ uname -a
Linux wellington 2.6.24-23-rt #1 SMP PREEMPT RT Wed Apr 1 23:40:34 UTC 2009 i686 GNU/Linux

The kernel I am using is linux-image-2.6.24-23-rt, package version 2.6.24-23.52.
I have had problems with linux-image-2.6.24-24-rt but have not had time to characterise or report them.

On this setup I am running dvb drivers from the v4l hg,
{{{
$ sudo modinfo dvb_usb_cxusb
filename: /lib/modules/2.6.24-23-rt/kernel/drivers/media/dvb/dvb-usb/dvb-usb-cxusb.ko
license: GPL
version: 1.0-alpha
description: Driver for Conexant USB2.0 hybrid reference design
author: Chris Pascoe <email address hidden>
author: Michael Krufky <email address hidden>
author: Patrick Boettcher <email address hidden>
srcversion: 42696397EE37DD79A9589B7
alias: usb:v0572p86D6d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB98d*dc*dsc*dp*ic*isc*ip*
alias: usb:v07CApA868d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB71d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB70d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB78d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB59d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB58d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB55d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB54d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB11d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB10d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB01d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB00d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB51d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pDB50d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pD501d*dc*dsc*dp*ic*isc*ip*
alias: usb:v0FE9pD500d*dc*dsc*dp*ic*isc*ip*
alias: usb:v1660p0932d*dc*dsc*dp*ic*isc*ip*
depends: dvb-usb,dib0070,usbcore,dib7000p
vermagic: 2.6.24-23-rt SMP preempt mod_unload 586
parm: debug:set debugging level (1=rc (or-able)). (int)
parm: adapter_nr:DVB adapter numbers (array of short)
}}}

The last time I pulled and built (Sat Sep 5 11:00:22 EST 2009), I got:
2b49813f8482 tip

See dmesg.working for dmesg output while the system boots, tunes to a live tv channel and then I log out.