Windows Defender on Vista (64 bit)

An interesting error occurred on my desktop with the Vista 64 bit during the
first part of December '07.

For the first time since Vista was loaded (about 1 October) I thought that I
would start Windows Defender and scan the computer. This would be the first
time in over two months. I got the following message:
-----------------------------------------
Windows Defender ---

Application failed to initialize: 0x800106ba. A problem caused this
program's service to stop. To start the service, restart your computer or
search Help and Support for how to start a service manually.

-----------------------------------------

So I rebooted. Got the same message. So I went to the various places on
the internet trying to find a solution to start Defender. None have worked
so far. There were a lot of threads on XP, but I only found one on Vista.

I even uninstalled MS Update <KB931099>, which was suppose to be a complete
new Win Defender install and then reinstalled it again (with a reboot in
between). No soap either with this change. Everything works OK on the
desktop so I have gave up to find a solution at that time.

I checked my laptop (Vista 32 bit) and defender works as it should. I could
always go back to the repair of Vista on the desktop and I might do that
sometime in the future. Any help or comments would be appreciated.

Thanks!

Bquinn