ftp install wants to retrieve $ROOT /RedHat/base/netstg2.img, which doesn't exist in 6.1.92. Probably the same problem on all arches (didn't try on anything but alpha yet though).
Just checked it - the problem is present on alpha and sparc. They still have a common stage2.img, x86 has netstg2.img and hdstg2.img. (But the installer tries to get netstg2.img on all arches)
should work with piglet-0218 (note that sparc and alpha are still having problems unrelated in ftp installs)