I've tried the method you're using as well. As I continued to strip code away in an attempt to remove possible causes, I noticed that just including the Ethernet.h library in 0022 requires me to include the SPI library. As soon as I include SPI.h, I get the same error I was running into before:
/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet/Dhcp.cpp:5:21: error: types.h: No such file or directory
I can't seem to get rid of this "types.h" error.