Well, got it working. An Arduino Ethernet Shield with a W5100. Without any modification to the hardware (also the INT not connected). Got to get used to that .NET Framework. Some strange things are happening. When a compile fails, the last good compile is put in the Netduino. So I made a blink-example, and after that a Ethernet example, but that didn’t compile well, so the blink-example kept beeing uploaded to the board. Will have to do a very good study of the C language that is used. Now several shields are working. LCD-keypad shield, Servo-shield and now the Wiznet ethernet shield.