DViCO FusionHDTV DVB-T Hybrid card can't tune in newer releases

I've been trying to track down a driver regression in my DViCO FusionHDTV DVB-T Hybrid card that makes it impossible to tune to DVB stations. In recent kernels (anything in past two years) the card is detected and /dev/dvb tree is created but attempting to scan for channels only results in a 'tuning failed!!!'.

Note: On some occasions the card will not be auto-detected correctly (usually warm boot), so I have added "options cx88xx card=46 tuner=72" to /etc/modprobe.d/dvb.conf.

After some investigation I found a comment on https://help.ubuntu.com/community/MythTV/Install/Gutsy/Tuners that indicated that the card stopped working around the release of Gutsy 7.10. Since I had an old LiveCD on hand, I tried out Feisty and found that the card tuned fine, but in newer releases the tuning fails.

Grabbing a few different kernel releases I can see that tuning works quite happily on the 2.6.17 kernel (very old) but appears to have broken somewhere around 2.6.22. Bisecting the v4l-dvb tree has the card turning at r4675, unable to compile r4676 and r4677, then no /dev/dvb tree being created until r5333 where tuning no longer works.

I'm a bit stuck at this point since debugging linux kernel drivers is a bit over my head, but I do have a test box which I can happily mess around with.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: linux-image-2.6.32-21-generic 2.6.32-21.32
Regression: Yes
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.32-21.32-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-21-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ubuntu 3290 F.... pulseaudio
 /dev/snd/controlC1: ubuntu 3290 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf5000000 irq 16'
   Mixer name : 'C-Media CMI9880'
   Components : 'HDA:434d4980,00010083,00090002'
   Controls : 21
   Simple ctrls : 12
Card1.Amixer.info:
 Card hw:1 'CX8811'/'Conexant CX8811 at 0xf1000000'
   Mixer name : 'CX88'
   Components : ''
   Controls : 3
   Simple ctrls : 2
CurrentDmesg:
 [ 50.079091] [drm] nouveau 0000:01:00.0: Allocating FIFO number 1
 [ 50.088059] [drm] nouveau 0000:01:00.0: nouveau_channel_alloc: initialised FIFO 1
 [ 50.314299] skge eth0: Link is up at 1000 Mbps, full duplex, flow control both
 [ 50.315802] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
 [ 60.508022] eth0: no IPv6 routers present
Date: Sun Apr 25 03:15:48 2010
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
LiveMediaBuild: Ubuntu 10.04 "Lucid Lynx" - Release Candidate i386 (20100419.1)
ProcCmdLine: BOOT_IMAGE=/casper/vmlinuz noprompt cdrom-detect/try-usb=true persistent file=/cdrom/preseed/hostname.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
RelatedPackageVersions: linux-firmware 1.34
RfKill:

SourcePackage: linux
dmi.bios.date: 09/02/2004
dmi.bios.vendor: Award Software International, Inc.
dmi.bios.version: F4
dmi.board.name: 8I915P Pro
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.type: 3
dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF4:bd09/02/2004:svn:pn:pvr:rvnGigabyteTechnologyCo.,Ltd.:rn8I915PPro:rvrx.x:cvn:ct3:cvr: