application failed to initialize: 0x80070002 (Windows Defender)

I successfully upgraded one more PC to Vista last week which was earlier running with Windows XP SP2 without any problems. Also Vista is working good except one thing, Windows Defender. Whenever I start my computer, I use to get two different errors every time. Those are:

“Windows Defender can't be started. Try again later”
And
“Application failed to initialize: 0x80070002.”

I thought re-installing windows defender can fix the error but system wont allow me to install or re-install and says Windows Defender is already installed. I thought if I could get any fix from Windows Updates but there was nothing helpful too.

I don’t have any idea how can I get rid of this error. Somebody please help.

Even I’m struggling with the similar error but I wont get it on startup. I get it whenever Win Def tries to scan the system. I’ve posted my query in another thread and will let you know if I got anything working. But there are few similar discussion available you should check them, they may help you as your problem is bit different from me:

http://forums.techarena.in/vista-help/1157469.htm
http://forums.techarena.in/vista-help/755898.htm
http://forums.techarena.in/vista-help/721291.htm

I thought I was alone with this problem but here seems many people facing it. Even am getting error code 0x80070002 with Windows Defender on Vista. I guess Vista is not compatible with WinDef or vice verca. In order to get some help regarding this I even tried contacting MSFT support but haven’t replied me yet, its been four days.

So remporarily, I have started using third party antispyware and its working good. If MSFT dint replied, I’ll better continue with this application itself.