nRF24l01 modules not working.

Hi, everyone.

I have been trying to get the nRF24L01 modules communicate with each other and I have used the code on this site: http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo. But, all I am getting is "No Radio Available" on the serial monitor. I also tried using the Mirf Library and still the results are same. I am positive that my connections are good and I am using separate power supply for the modules.

Please Help.