Keep loosing my ATT Yahoo Toolbar?

For some reason i keep loosing my ATT Yahoo toolbar. I have to keep reinstalling it when i go to another web page. I come back to my Yahoo Home Page & the toolbar is gone. I then have to d/ & install it again. It happens all the time. What's causing this? I've uninstalled Yahoo & reinstalled it but it keeps happening. How do i prevent it from doing this?