Internet is fine. I start browsing, and it goes down.

Windows 7, 64 bit. Connected through router. Internet works fine. There are downloads and updates going on, no problem. The moment I start browsing, everything goes down and there's no browsing or downloading or any activity. It remains this way for a few minutes then comes back up. It keeps happening over and over again.

I'd really appreciate any help I could get for this strange problem.

Is this only affecting this one PC or are there others having the same problem. The first thing that comes to mind would be malware. Have you updated your Antivirus and scanned the PC. You also may want to visit the Malware Forum (see link below)
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Thanks. Yep, scanned using MSSE and Malwarebytes. I'm not sure if others are having the same problem.