Internet suddenly stopped working :/

Hi there, I was hoping you guys could help me out with an internet problem.

My computer is connected to a router (specifically a Motorala SURFboard SB5100) via a USB connection. For the longest time, it was connected to my computer, and networked via ethernet from my computer to my dad's PC, allowing shared internet. A couple of weeks ago, the PSU on my own computer died, and during the computers downtime, I took the ethernet from my PC and connected it directly to the router, allowing the internet on my dad's PC.

When I replaced the PSU, everything was back to normal, except the internet no longer works on my PC. I reformatted the HDD, and tried the set up the internet the way I always have done, and it still doesn't work. An icon appears saying 'aquiring network address' and then after 60 seconds or so the yellow exclimation mark symbol appears and says 'limited or no connectivity'. I've tested all the USB ports, they work fine with every other device.

Anyone know what the problem might be and how I can solve it? I'm running on Windows XP (both computers) btw.

EDIT: Forgot to mention, I also tried connecting the router to my own PC via the ethernet cable aswell...exactly the same thing happens.