mrkcee
are you using a adsl modem ? before i moved to cable broadband i was on a adsl usb modem and had the same thing happened to me for weeks , found out in the end it was the drivers for the modem .
downloaded new drivers and had no problems after that .
another problem i had with my new pc was because it had hyper threading enabled it kept rebboting my pc when using a cable modem on the usb connection , changed to nic and that solved the problem hope this helps