After doing a lot of research about ad.yieldmanager, I've learned it is a tracking cookie that can keep coming back even after you've removed some of the bad stuff from your system. It can come back when you visit certain web pages. For me, it's been ebay.com and a univision.com web page.
Cookies are text files placed on your computer by various sites that you visit either directly (first-party) or indirectly (third-party). A cookie can contain any data that a site wishes to store. It is often used to track your computer as you move through a web site and store information such as preferences or credentials.
Another help site suggested changing my web browser security to minimize cookies.
So I went here... http://www.us-cert.gov/reading_room/securing_browser/
and made some
of the changes they suggested. I say some
because when I set my browser security to High, I wasn't able to run some programs or access some websites. For example, when I logged into to the bleepingcomputer forum and came to this thread, it wouldn't let me make a post. And when I went to login into my Imageshack account, it wouldn't recognize me. But when I set the security to Medium and added Imageshack to my allowed sites under Privacy, those problems went away.
After making these changes, this is what I got when I went to ebay (see screen capture)... http://img185.imageshack.us/img185/9753/adyieldebayro2.jpg
It asks if I want to allow the ad.yieldmanager cookie!!! So I clicked "No" to deny it, and was able to surf ebay without any more problems from ad.yield manager.
Not sure if this is a definite fix... only time will tell.