TV Tuner failing after SP1 install on Vista Ultimate

I am having problems with Windows Media Center not playing live video after
installation of Vista SP1.

The tuner card and video were working great right up until the install of
the Service Pack, and started failing immediately after the installation.
All functions of the WMC seem to work OK, with the exception of anything
dealing with the tuner card.

Configuration is as follows:

Tuner: ViXS Systems Inc. - ViXS Pure TV-U 4899 (NTSC/ATSC Combo)
OS: Vista Ultimate Edition
Machine: Gateway GM5420

Errors: When Attempting to start Live TV, separate message box pops
up stating:
"Windows Media Center Receiver Service has stopped
working"
Details show:
APPCRASH in ehRecvr.exe (version 6.0.6001.18000)
Fault Module Name StachHash_8a90
Exception Code: c0000374
OS Version: 6.0.6001.2.1.0.256.1


In the Media Center pane, I eventually get the message:
Tuner Not Installed - Video cannot be displayed because
no tuner hardware has been detected.
Please check that your tuner hardware is properly
installed.

I checked device manager in computer management and there were no flagged
items and it says the tuner is working properly.

I tried doing a System restore to back off the SP1, but the problem
remained. I upgraded the drivers with the latest available from the Gateway
support site, but the problem remains.

I tried pulling the card out and deleting the hardware from the
configuration (deleting the drivers while doing so), and re-installing the
card with the new drivers, but the problem remains.

Gateway's stance is they will never support a machine other than with the
original configuration (and anti-virus programs should eliminate the need
for any service pack upgrades to prevent viruses). I'll say here an now
that this is the last Gateway machine I will ever buy, due to their poor,
pig-headed, script-kiddy tech support.

Does anyone have any other suggestions to try before I go in and wipe the
machine and try re-installing everything from scratch?