I guess you probably have this solved. But for others who are having problems....
If you want to use M-PC on your existing network without changing to 2.x.x.x addresses simply:
Go to the Menu
Select EtherDMX on Left column
Then ArtNet along the bottom
Artnet - ON
Discovery - Full broadcast [This actually wont work if you select any other option here]
Override - ON
IP Address - [Enter your target IP address here for your artnet controller]
I am successfully using this to switch between testing using Chamsys MagicVis [which MUST be located on another PC] and my Entec ODE.
Hope that helps!