I can't get my Leonardo to run with RFM12B when I am using the jeelib library [GitHub - jeelabs/jeelib: JeeLib for Arduino IDE: Ports, RF12, and RF69 drivers from JeeLabs]
Even if everything is disconnected and it's just the leonardo board itself the library seems to prevent the USB/Serial Connection from working.
The only thing I can do is force it into this special reset mode where it is reachable for 8 seconds to program another sketch where the Serial connection works, but like i said it's just another sketch just to get the USB/Serial connection back to work, not the one i actually want to have on the leonardo.
I am using the RX/TX examples from the jeelib library. Both work on the Arduino UNO but the Leonardo can't handle it 
Here is the code example for the receiver
//Simple RFM12B wireless demo - Receiver - no ack
//Glyn Hudson openenergymonitor.org GNU GPL V3 12/4/12
//Credit to JCW from Jeelabs.org for RFM12
#define RF69_COMPAT 0 // Set to 1 if using RFM69CW or 0 is using RFM12B
#include <JeeLib.h>
#define myNodeID 30 //node ID of Rx (range 0-30)
#define network 210 //network group (can be in the range 1-250).
#define RF_freq RF12_433MHZ //Freq of RF12B can be RF12_433MHZ, RF12_868MHZ or RF12_915MHZ. Match freq to module
typedef struct { int power1, power2, power3, battery; } PayloadTX; // create structure - a neat way of packaging data for RF comms
PayloadTX emontx;
const int emonTx_NodeID=10; //emonTx node ID
void setup() {
rf12_initialize(myNodeID,RF_freq,network); //Initialize RFM12 with settings defined above
Serial.begin(9600);
while (!Serial);
Serial.println("RF12B demo Receiver - Simple demo");
Serial.print("Node: ");
Serial.print(myNodeID);
Serial.print(" Freq: ");
if (RF_freq == RF12_433MHZ) Serial.print("433Mhz");
if (RF_freq == RF12_868MHZ) Serial.print("868Mhz");
if (RF_freq == RF12_915MHZ) Serial.print("915Mhz");
Serial.print(" Network: ");
Serial.println(network);
}
void loop() {
if (rf12_recvDone()){
if (rf12_crc == 0 && (rf12_hdr & RF12_HDR_CTL) == 0) {
int node_id = (rf12_hdr & 0x1F); //extract nodeID from payload
if (node_id == emonTx_NodeID) { //check data is coming from node with the corrct ID
emontx=*(PayloadTX*) rf12_data; // Extract the data from the payload
Serial.print("power1: "); Serial.println(emontx.power1);
Serial.print("power2: "); Serial.println(emontx.power2);
Serial.print("power3: "); Serial.println(emontx.power3);
Serial.print("battery: "); Serial.println(emontx.battery);
Serial.println(" ");
}
}
}
}