You will have to edit the script provided by Jeff to replace dhcp-client with dhcp3-client in the extra_packages line. It seems the package name has changed in emdebian.by popel_ok - Debian
Dear moddy, I encountered the same problem with my sheevaplug and according to an intensive search in several fora the problem is the timing of the uboot. Your external USB HDD is too slow in responding and thus it is not ready to be choosen after a hard reset. The soft reset keeps the USB HDD spinning and it is responding more quickly. The solution is to add a delay in the uboot configuratiby popel_ok - Debian