If you PXE boot a machine that uses the via-rhine driver in Linux you will find that you can boot it only once. After that first boot you have to physically remove power to the box to restore the network controller to the proper state. Well, at least that is the behavior I see with my VIA M10000 board.
As a workaround I commented out the following line in via-rhine.c on or around line 1969
iowrite8(ioread8(ioaddr + StickyHW) | 0x03, ioaddr + StickyHW);
Ahh, once again my Myth frontend reboots!