Hardware Network/Router Trouble

[Jamstruth]

I'm having a massive problem with my internet at the moment and unfortunately for my flatmate I seem to have tracked it to his brand new desktop PC.
Earlier tonight as soon as the wire for his PC was plugged in the internet ground to a halt. The Router, which had been getting a 1.6Mbps downstream all day (yeah our internet sucks. We need to get it changed) suddenly disconnected and when we restarted the router it was down and 0.6Kbps. Sounds like something on the ISP end, I know, but it is definitely to do with his computer. Eventually the computers just wouldn't connect to any site but for some reason Skype worked just fine.
Installed Wireshark on his computer and took a couple of log files (I can upload if you would like). The first highlighted an IP checksum problem, we went into the system and disabled all IP checksum offloads and the 2nd log showed no black entries. Now its back working again but not very quickly. When his computer wasn't plugged in I got a 1.5Mbps SpeedTest.net downstream, now its 0.25Mbps.

I'm no network guy so any ideas what the hell could be going on. Near as I can tell its not a "Packet Storm" (something I've heard off that can ground networks to a halt) as there's no constant repeating packets in the logs.

 

[Xarsah16]

Have you verified your MAC address (on both computers) with the ISP? I remember that before I did this, when I was trying to plug in a new, wired, cable router, I was unable to connect to the internet at all. Very basic thing, but it could be your solution...

Try giving your ISP a call and see what they suggest.

 

[Jamstruth]

Never had an issue with MAC verification before. In this age it doesn't make any sense to want to do something like this. My laptop, his laptop, my phone, my iPod, my Xbox all work fine over either of the Routers we ahve (they gave us one, I thought it was a piece of crap and we started using an old one of mine. This problem covers both routers).
Also I uploaded the Wireshark logs
https://docs.google.com/open?id=0Bz8D6d_ZJ6WwVXNJaEV1M2ZRcW8
https://docs.google.com/open?id=0Bz8D6d_ZJ6WwdmE1X0xoSkZ3Tk0

Update: Its actually probably some kind of hardware defect. Going to contact our ISP and see if they have any records of us having our speed throttled though (definitely seems to be their end. Router reports the slower speeds in its DSL downstream). If they have been throttling us they can at least explain why and if its anything actually wrong with the computer or just that my friend's MAC address was somehow flagged.