2008.0_beta1 minimal cd only has the e1000 kernel module compiled. Please include also the e1000e driver (for PCI-express cards) in x86 and amd64 configurations.
This driver is enabled for amd64/x86 in the 2008.0 Beta 2 kernel configs, so it should work when that CD is released in the next few days. Please test it and let us know.
It works with 2008.0_beta2.