iMac Freezing with Cincinnati Bell Fiber Optics

I have a five year old iMac desktop computer. I recently received Fiber Optics service from Cincinnati Bell. As soon as I had gotten access to the internet, the computer froze and shut down. Now any time I try to access the internet, the iMac will do the same thing over again, freeze and shut down. I was with TWC previously and never had issues in this regard. Are there any other users experiencing this with iMacs and fiber optics or with Cincinnati Bell?