Ethernet shield on a Mega with a 433 mhz receiver

I have set the mega and the 433 to receive on pin 18 (interrupt 5) also i0=pin2 or i1=pin3. They all work and receive messages from the sender all the time. The moment i connect the ethernet shield on top of the arduino mega no interrupt works anymore ! I am forced to get the vcc pin of the 433 receiver on the ethernet shield as it is "ported" there and tried all the interrupts possible on the mega . None works ! The moment i disconnect the shield interrupt starts working (I can see led blinking on the mega as it receives messages).

Can anyone help ? It is a simple question I hope there is no need for a code ! I am new so it may have something to do with spi and interrupts on the mega interfering ... Thanks

Post links to the ethernet shield and the 433 mhz receiver.
Also post your code.

Shield : http://arduino.cc/en/Guide/ArduinoEthernetShield
433: http://dx.com/p/433mhz-rf-transmitter-module-receiver-module-link-kit-for-arduino-arm-mcu-wl-green-220194#.UvvowYWY8gQ

CODE :

#include <SPI.h>
#include <Ethernet.h>
#include <RCSwitch.h>

int led = 13;
RCSwitch mySwitch = RCSwitch();

void setup() {
Serial.begin(9600);
pinMode(led, OUTPUT);
mySwitch.enableReceive(5);
}
void loop() {
if (mySwitch.available())
Serial.println(“ERR”);
mySwitch.resetAvailable();
}

Now I see I followed the led from the mega and the serial output as evidence of incoming data BUT did not actually blink the onboard led ! I suspected that actualy the SPI connection between the mega and eth shield was interrupting the Serial communication to the PC so I have added code to blink the onboard led to see incomming data. And it blinks with ethernet shield on top no problem . The only problem I can see is that nothing can be sent to the pc over serial communication ... hence no TX blinking on the mega and no outpu on the screen ... Why could that be ?

Latest data.... In fact it works :) Now I can also see it on the pc... I have plugged in additional power supply. It was only connected to the USB.... maybe there was not enough power...

Thanks ...