Make sure the rf24 power supply can provide enough current. I use homemade adapters like these. They are powered by 5V and have a 3.3V regulator on the board.
If using the high powered radios make sure to separate them by a few meters. The may not work too close together.
Reset the radios by cycling power to them after uploading new code. I have found that to help. They do not reset with the Arduino.
Switch to 1MB data rate to catch the not so cloned clones.