Constant game lagging after downloading?

[Erratic Fox]

Every time I download something that has a size of about 1 - 3 Gigs, my multiplayer game play lags. I play Xbox Live. I know it has nothing to do with Xbox Live. My download rate is around 27 Mbps and upload is around 7mbps. I had no lag all week this week, until I downloaded a iso that was around 2.7 Gigs today. After that, my Xbox Live connection has been horrible. I really don't know why. Nothing else is going on. Everything else is fine, except my Xbox Live. I downloaded (the ISO) through Firefox. So does something keep running in the background that does this? I've tried numerous thing, I usually just wait a day, and it's fine again. So what could be causing this? It has nothing to do with ports either. Because it only happens after a big download.

 

[AstaLaVista]

Have you tried restarting your PC after the download is finished? or even better... shut it down for a few secs and start it again...

Plan B or Worse case... shut the PC down and test MP to see if that gets rid of the problem.

Other than that... I'm stumped!