League Freezes

For whatever reason my leauge is sucking so bad right now. It's actually causing my computer to stall. I could use my computer for 16 hours flawlessly, but on game of league and it's guaranteed to freeze. Like a really hard freeze, 2-4 seconds of complete inactivity. It happens mostly during team fights and never freezes outside of league. Also it seems my ping doesn't change and I've tried to reinstall it without success. I've also tried to clean out my Registry and defraged my computer which is roughly 4 years old.