atmega2560 board and rfm12b module losing messages

Hello,

I 've got the RFM12B module working with the mega2560 cpu.
I sent every second from a jeenode to mega2560 (1 meter distance) and viceversa a package via the pingpong example.
But on the mega2560, I loose 90% off the messages (coming from jeenode). Sending is correct from mega2560 to the jeenode (jeenode receives every sec a message).

When I replace the mega2560 to the duemilinavo, it works perfect.
I change the pins :
on atmega328 pin 2 --> atmega2560 pin 2 (IRQ)
on atmega328 pin 10 --> atmega2560 pin 53 (SS)
on atmega328 pin 11 --> atmega2560 pin 51 (MOSI)
on atmega328 pin 12 --> atmega2560 pin 50 (MISO)
on atmega328 pin 13 --> atmega2560 pin 52 (SCK)

I use Arduino-0021 and the latest port and rf12 library.

I've already changed the rf12.h library (Atmega1280 to ATmega2560) :
// pins used for the RFM12B interface
#if defined(AVR_ATmega2560)
#define RFM_IRQ 2
#define SPI_SS 53
#define SPI_MOSI 51
#define SPI_MISO 50
#define SPI_SCK 52
#else
#define RFM_IRQ 2
#define SPI_SS 10
#define SPI_MOSI 11
#define SPI_MISO 12
#define SPI_SCK 13
#endif

and the ports.cpp (comment the sleepy parts (see thread )) (see thread ???)

Anyone an idea ? How should I further debug it ?
Could it have to do with the IRQ pin ?

Thanks in advance, Jeroen.