Ethernet library won't compile for custom hardware

As the subject-line says, I can't compile sketches using the Ethernet library in Arduino 1.0 for a custom board, whose hardware definition is in ~/Documents/Arduino/hardware/OpenLCB I get the following errors:

/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avr-g++ -c -g -Os -Wall -fno-exceptions -ffunction-sections -fdata-sections -mmcu=at90can128 -DF_CPU=16000000L -DARDUINO=100 -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/cores/OpenLCB -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/variants/OpenLCB -I/Applications/Arduino.app/Contents/Resources/Java/libraries/SPI -I/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet /var/folders/+Z/+ZVggXdSHbW9VypYQpUaIE+++TI/-Tmp-/build1183822088658838250.tmp/WebServer.cpp -o/var/folders/+Z/+ZVggXdSHbW9VypYQpUaIE+++TI/-Tmp-/build1183822088658838250.tmp/WebServer.cpp.o 
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avr-g++ -c -g -Os -Wall -fno-exceptions -ffunction-sections -fdata-sections -mmcu=at90can128 -DF_CPU=16000000L -DARDUINO=100 -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/cores/OpenLCB -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/variants/OpenLCB -I/Applications/Arduino.app/Contents/Resources/Java/libraries/SPI -I/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet -I/Applications/Arduino.app/Contents/Resources/Java/libraries/SPI/utility /Applications/Arduino.app/Contents/Resources/Java/libraries/SPI/SPI.cpp -o/var/folders/+Z/+ZVggXdSHbW9VypYQpUaIE+++TI/-Tmp-/build1183822088658838250.tmp/SPI/SPI.cpp.o 
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avr-g++ -c -g -Os -Wall -fno-exceptions -ffunction-sections -fdata-sections -mmcu=at90can128 -DF_CPU=16000000L -DARDUINO=100 -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/cores/OpenLCB -I/Users/dgoodman/Documents/Arduino/hardware/OpenLCB/variants/OpenLCB -I/Applications/Arduino.app/Contents/Resources/Java/libraries/SPI -I/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet -I/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet/utility /Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet/Dhcp.cpp -o/var/folders/+Z/+ZVggXdSHbW9VypYQpUaIE+++TI/-Tmp-/build1183822088658838250.tmp/Ethernet/Dhcp.cpp.o 
In file included from /Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet/Dhcp.cpp:4:
/Applications/Arduino.app/Contents/Resources/Java/libraries/Ethernet/utility/w5100.h:100: error: expected unqualified-id before numeric constant

The code in hardware/OpenLCB/cores/OpenLCB is a fresh copy of all the files in Arduino.app/Contents/Resources/Java/hardware/arduino/cores/arduino/

Sketches using Ethernet compile just fine for the Uno or any other built-in hardware supported boards. The only relevant software differences between the Uno and my boards is in boards.txt, and variants/.../pins_arduino.h

(The reason the core files are alike is to try to get the sketch to compile; there are, of course, some significant differences in the hardware that should be reflected in the core files, but I'll go back and add those changes back in once I see why the Ethernet library is causing me problems.)