Thanks so much for this thread!!!!
I had to register here, just to say to all of you who posted the solution, thanks!!!
Today, I was forced to download the new version of the Yahoo Music Engine so I could access my subscription music. After I did, the computer would no longer be able to open multiple internet explorer windows. Same as has been discussed here. I tried doing everything, and nothing worked 
So with a little help from Google, I came to this wonderful thread, which solved my problem. Apparently, the Yahoo Music Engine was [sarcasm]so kind [/sarcasm] as to install the Yahoo toolbar without my permission.
Thanks, Yahoo!!! 
You guys rock! And now these forums go to my favorites.....