Getting a bogus IP address that is not 127.0.0.0 makes me ask whether you may have had a different Ghost server on the network in the past, or whether the IP address you are getting is valid for any part of your organisation. If you have a test server somewhere on the network that is running another DCHP service, it could be issuing an invalid IP.
If all that checks out then I would focus attention on the NIC driver. The WinPE version used in GSS 2.5.1 is V2, based on the 32 bit Vista kernel, so requires the addition of Vista 32 bit drivers via Ghost Boot Wizard. These two articles may be of help:
http://www.symantec.com/business/support/index?page=content&id=TECH110134
https://www-secure.symantec.com/connect/articles/do-i-have-correct-driver-winpe
PXE booting initially uses the NIC bios to get the first blocks from the TFTP server, but once the WinPE image gets loaded, it is the installed WinPE NIC driver that takes control. If this is not working for some reason then it would affect the ability to get a working connection.