Javascript error with window.external.AddFavorite

Hello,

We just noticed that whenever we try to do a call to
window.external.AddFavorite we get the error "Object doesn't support this
property or method".

I'm not totally sure when it showed up, but we noticed it in late last week.
 We are using IE7.  For me, I'm using Windows XP Service Pack 3.  I am not
sure what is the configuration of our customer's machines, but mine is up to
date.

Some more info on this issue:
I have gone to several different websites to make sure this is an issue with
our browser.  For example:
http://www.yourhtmlsource.com/javascript/addtofavorites.html
http://www.dynamicdrive.com/dynamicindex9/addbook.htm
http://www.htmlgoodies.com/beyond/dhtml/article.php/3470451
http://www.w3schools.com/js/tryit.asp?filename=tryjs_bookmark

In addition, I tried searching around the net but did not see anyone else
running into this issue.  Lastly, I downloaded the Virtual PC and got an
image for XP IE7 from here:  
http://www.microsoft.com/downloads/details.aspx?FamilyId=21EABB90-958F-4B64-B5F1-73D0A413C8EF&displaylang=en

It works fine on the image.

Do anyone know of some patch to IE/Windows that could have caused this
issue?  Maybe some other software that could be causing the issue?

Thanks in advance