Uh... Did you try turning it off and on?Nothing should be taking up that much bandwidth here, so either we had a lot of traffic at that time or you're just unlucky...Is it still doing it?
Your browser stores information from all of the webpages you have been using, so when you leave it running for a long time, it will get slower. It is kinda like the memory leak bug that happened with Fallout New Vegas on Xbox, where the loading times would take forever because it was trying to store too much information, and you had to restart your console every couple of hours.