ETHERNET SHIELD RFID PROBLEM

Projects Networking, Protocols, and Devices
2
  1. Sending data alone without an RFID works.
  2. Defining SDA and RESET of RFID to pins 8 and 9 respectively. ..........
    COMPONENTS USED:
    Arduino MEGA 2560

Mega's I2C is on pins 20,21. I don't think you can change it, I don't know how you would try, and why would you want to?

As I have read online, there seems to be a problem with the SPI usage. I would like to ask if it is really the SPI being the root cause of the problem.

I recall there is some problem with library support of the various buses. Does your library support SPI?