Sounds like it isn't totally happy with the NIC driver so isn't getting an address from DHCP after which everything network based would fail.
Have you look at SP3 which will use the later version of WinPE so you can use Win7 drivers?
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As MarXtar pointed out, I would definitely try another Vista driver for that NIC. Either go with a newer one or find an older one that might work. Unforunately sometimes it is hit or miss with drivers. Going to SP3 would also help for the reason stated above.