Hi Jantje,
I had the same problem as Globe.
When compiling the libraries i got the following errors:
**** Build of configuration Release for project ETHERNET_Test ****
make all
Building file: C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.c
Invoking: AVR Compiler
avr-gcc -I"C:\Program Files\arduino 1.0.2\hardware\arduino\cores\arduino" -I"C:\Program Files\arduino 1.0.2\hardware\arduino\variants\mega" -I"C:\Program Files\arduino 1.0.2\libraries\Ethernet\utility" -I"C:\Program Files\arduino 1.0.2\libraries\Ethernet" -I"C:\Program Files\arduino 1.0.2\libraries\SPI" -I"C:\Program Files\arduino 1.0.2\libraries\Wire" -I"C:\Program Files\arduino 1.0.2\libraries\Wire\utility" -D__IN_ECLIPSE__=1 -DARDUINO=102 -DUSB_PID= -DUSB_VID= -Wall -Os -g -mmcu=atmega2560 -DF_CPU=16000000UL -MMD -MP -MF"Wire/utility/twi.d" -MT"Wire/utility/twi.d" -c -o "Wire/utility/twi.o" "C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.c"
C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.c:115: error: conflicting types for 'twi_readFrom'
C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.h:45: error: previous declaration of 'twi_readFrom' was here
C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.c:192: error: conflicting types for 'twi_writeTo'
C:/Program Files/arduino 1.0.2/libraries/Wire/utility/twi.h:46: error: previous declaration of 'twi_writeTo' was here
make: *** [Wire/utility/twi.o] Error 1
**** Build Finished ****