Hi,
A friend had this very same issue yesterday.
I rebooted the modem a few times, same for the PC, reset the stacks (both IP and Winsock), updated the ethernet driver, checked the service pack revision and continued to not get a DHCP address.
My Laptop was able to get an address, but was pointed to their website to sign up as a new user.
I brought the "bad" laptop to my place and it worked perfectly using the same cable and ethernet card. This would to me seem to eliminate the stack, cable, card, et al.
I'm unfamiliar with DSL modems boot operation, but a cable modem boots up, POSTS, looks for the downstream, registers on the upstream, grabs the config file via TFTP, loads the config file then allows the CPE to "register"
Verizon is sending a new modem to try, but color me skeptical.
Does the DSL modem have a config file? Does it store registration info?
My next thought would be to put a different card in his laptop (pcmcia) and attempt to circumvent the issue. but that doesn't explain where the hang up is in him getting an IP address.
I may place a hub on the modem and capture the transaction with wireshark.
Best guess? I think the MAC address of his ethernet card is still "registered" with either the modem, or their head end and has gotten into a bad state. He took a power hit at the house that lasted a whole 3 seconds. Sounds like it's not as unique an issue as it appears.