Jinn

I bet I know what this is! I had an almost identical problem on my setup a few weeks ago, but with three PCs on the network. It would work find, but it felt like it dropped every few seconds to really slow, and then came back to full speed.

Start> Run these:
Watch the ping times. If you're getting a huge drop at a certain IP, find out who owns that IP. If its your ISP, ask them specifically if there's an issue at that IP.

For me, however, it was a virus. There was a recent FF exploit that let virus drop into a hidden folder in Program Files directory, and it tried to DL some stuff from about 12 different "hacker" sites every 9 ms. Watching my ping, I saw this.. 30.. 30.. 30.. 30... 30. 1209.. 30... 28... 28... 30... 2014...

Ran Symantec, Adaware, and Spybot -- you might be surprised that you've got a virus eating up bandwidth trying to propogate itself.

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"I'm typing on a computer of science, which is being sent by science wires to a little science server where you can access it. I'm not typing on a computer of philosophy or religion or whatever other thing you think can be used to understand the universe because they're a poor substitute in the role of understanding the universe which exists independent from ourselves." - Willravel