Moving SPI pin initialization from constructor to begin() function. That way, the SPI library won't alter any pin states unless / until you call begin().

Author: damellis

examples/BarometricPressureWebServer/BarometricPressureWebServer.pde

@@ -60,6 +60,9 @@ long pressure = 0;
 long lastReadingTime = 0;
 
 void setup() {
+  // start the SPI library:
+  SPI.begin();
+
   // start the Ethernet connection and the server:
   Ethernet.begin(mac, ip);
   server.begin();
@@ -68,8 +71,6 @@ void setup() {
   pinMode(dataReadyPin, INPUT);
   pinMode(chipSelectPin, OUTPUT);
 
-  // start the SPI library:
-  SPI.begin();
   Serial.begin(9600);
 
   //Configure SCP1000 for low noise configuration:

utility/w5100.cpp

@@ -25,8 +25,11 @@ W5100Class W5100;
 
 void W5100Class::init(void)
 {
-  initSS();
+  delay(300);
 
+  SPI.begin();
+  initSS();
+  
   writeMR(1<<RST);
   writeTMSR(0x55);
   writeRMSR(0x55);