You need a second try 
The SS signal is "active low", and SEN is "active high", so you need to flip the 1s and 0s in steps 3 and 4.
Set the Ethernet's SS to 0, and SEN to 1, to talk to the Ethernet. Set them opposite to talk to the RFM12.
Someone mentioned that the RFM12 driver is using interrupts. You'll need to modify that. You might be able to just disable that interrupt while talking to the Ethernet. Or you might need to make more complicated changes.
Ran