[Client] Slow interactivity/slows down whole computer

This started with the previous patch (the one before the shen update). Whenever I have the client open, (not in game, only the client), not only is interacting with the client lagging by ~5 seconds whenever I click anything, it slows down my ENTIRE computer. Alt-tabbing is usually instantaneous, for instance, when the client is open, it takes a good 1-2 seconds to switch. same with switching tabs on a browser. When I go from Queue to champ select, there is a 5-10 second lag between when the audio suggests I'm in the room, and actually having the interface pop up. Finally, after the game is finished, it usually takes between 1-2 minutes before it switches back from in game to the after-game information in the client, during which time I can't use the computer at all. This never used to happen.

There are also random occasional in game freezes lasting between 1-3 seconds, usually during attacks which are graphically intensive.

Windows 8.1 Intel 3570k 8gb ram Nvidia 750 TI