OK I've just made two changes to the OzTiVo Twiki.

In NetworkingHowTo I have changed this statement near the bottom of the page from:

There is no reason to change your MAC address unless you plan on running multiple Tivo's on the same network. All Turbonet cards ship with the same MAC address, and thats where the problem lies. So in the event that you are running multiple Tivo's, you will need to select a unique MAC address for each Tivo.
to:

If this is not your only TiVo on your network then it is a good idea to alter the MAC address of the network card, otherwise it is most likely your router will have problems assigning a network address to the TiVo and you will have connection issues. This is because by default all turbonets, terbonets, x-factor and TV-LAN1.0 cards have the same MAC address, all cachecards have the same MAC address and all AirNet cards have the same MAC address (note that means all three types have different MAC address from one another). Even if this is your one and only TiVo on the network you may consider doing this step anyway just in case you ever need to plug in another TiVo onto your network and forget about the MAC conflict.
And in PrepareTiVoDisk I have added that statement to the section about the networking menu.

I would have put in also the exact default MAC addresses for each card type but this escapes me for now.... and I must get to work!