This is a Tulip clone, which is listed in tulip.c, and according to Linksys' webpage worked in RedHat 6.0. The PCI identifier of the one I have is VID=0x11AD DID=0xC115 RID=37. See: http://www.linksys.com/support/solution/nos/linux_lne100tx.htm
You could try using the driver disk available at: people.redhat.com/notting/tulip/tulip-dd.img Boot the installer with 'linux dd', and use that disk when asked for a driver disk. Does that help?
This issue has been assigned to a developer for further action.
Try out the latest installer available in beta and tell me whether we have gotten it right this time.