You are turning the modem of at the mains for about 30seconds between changing from usb to ethernet aint ya...
from wot I remember, its suggested you turn the modem and router off for about 30 seconds, turn the modem on and wait for the lights to settle... and then the router... wait for the lights to settle on that.. then you can turn the comp on.
or was it router first, then modem... (always get the order mixed up)