I don't think a spyware cleaner could nuke the config off the 2wire. Most 2wire gateways are routers. Early models only had single RJ45. Later models had a built in 4 port switch for the LAN. As of a roughly a year ago they released a model that was a standalone unit, but the PPPoE was still handled in the modem. 2wire modems normall have 3 lights (top middle bottom) If the middle light is green, then the modem's PPPoE authentication is good. IF it is amber, you have sync, but no authentication. If red/unlit you have no signal from the inner pair.
But I digress... Make sure you disable software firewalls are disable so we can isolate them. Do you receive an error when trying to /release and /renew? The normal error of a damage TCP/IP stack from a spyware would mention the word "socket". A few fixes out there that will repair the TCP/IP stack including the one built into XP SP2. From a command line type "netsh winsock reset catalog" then reboot.
http://www.snapfiles.com/get/winsockxpfix.html if you don't have SP2.
If you are receiving an autoconfig ip 169.254.x.y please let us know. You can always run a system restore in XP and undo the damage if it was software related (not 100%) but that would reverse your clensing of the SPYware. Good luck and report back!