Help - MCX upgrade failed, now MCX-PC software install fails

I have a Linksys MCX which worked fine for months with my Dell MCE 2005
(running Norton Internet Security 2005) until I tried to do the MCX firmware
upgrade (wirelessly) which failed part way thru. After this, all
communication with the MCX was lost. Resetting the MCX did not help so I
tried to uninstall and reinstall the MCX PC software. Now the software will
not install and fails with:

"/Setup Error

The setup for the Media Center Extender was not successful. Please try
the installation again, or contact your hardware manufacturer for
assistance."

In Event Viewer (Application) it reports:

"Product: Media Center Extender -- Error 1904. Module
C:\WINDOWS\eHome\MRProxy.dll failed to register. HRESULT -2147024770.
Contact your support personnel."

On power-up, the MCX sees my wireless network and retrieves the SSID with
excellent signal strength and gives the setup key so it's not a network level
problem (I've also tried this with a wired connection). I've tried manually
registering the DLL with regsvr32 and got

"DllRegisterServer in C:\linksys\mrproxy.dll failed.
Return code was 0x8007007e"

I've tried unregistering it and deleting all instances of MRProxy and tried
to reinstall, I've tried system restore, I've run "sfc /scannow" and
"depends.exe" looking for something/anything, all with no luck. I've gone
thru hell with Linksys tech support who effectively washed their hands of it
and said it is a MS problem.

If anybody has any ideas I'd sure appreciate hearing them. My frustration
level is off the scale. Thanks.