Framerate keeps dropping

Let me start this off by saying I'm not the most tech savvy person around. Since the release of 3.1 I've found that my fps has been plummeting within some of the more populated cities in game and even in quieter areas when it wasn't an issue in the past. I've also noticed that when I tab out of my game to surf the web, webpages will load a lot more slowly. However, the moment I exit the game entirely, everything will go back to its normal speed. I'm not sure what's wrong, but I do know this hasn't happened before in the past.