Google Chrome/Internet Going Suuuuper Slow

A couple days ago, my internet suddenly started going incredibly slow (I'm on a high-speed cable line). I usually use Chrome, and after searching I found a possible solution to disable the "predict network actions to improve page load performance" option in Chrome's settings, and that seemed to work for a few minutes. After that, it slowed to a crawl again, and now it doesn't matter whether that option is on or not. I also tested with Firefox and found that Firefox is even worse. It struggles just to load the home page when I open it (which is google.com). Also, other computers and devices running off the same wireless router have no problems, so clearly there's something wrong with my computer.

My instincts tell me virus, but I've run Avast, Malwarebytes' Anti-Maleware, and SuperAntiSpyware, all of which are totally up-to-date, and they haven't found anything. When doing anything else internet related, the computer seems to be functioning normally. It's only when I open an actual web browser such as Chrome or Firefox that it gets wacky. I noticed in the task manager that my CPU is also pegging at 100% when I open a browser as well, so the whole system slows to crawl. Close the browser and everything is fine again.

Anyone have any idea? Are my instincts right that this is some kind of sneaky virus, or is it likely something else that's the culprit? Thanks in advance for any help.