Well mate, you can't insert an image here that is hosted on your own machine, you have to first upload it to a image hosting site.
Well a virus would certainly do it.
DNS is a bit of a long story if you dont already know, but basically it translates
www.google.com to 45.68.99.56 (just made those numbers up). It has to be in number form for the internet to work. If you have a slow dns server it will bottle neck your proccess. If you DNS is mad at you and just slows down when you start hammering it, then it would do what you described.
The thing here is if it happened when you were on someone elses inet connection then you would have to have your dns servers programmed into your pc software, rather then pulling them dynamically from your isp.
Anyway, thats a simplified explanation, and its unlikely that it is your DNS, I just wanted to cover a broad spectrum of things you could check. Google how to change your dns and what it is for more info.