problem arduino as master for home automat


I am struggeling for 2 months now with the following, please help me:

I run a arduino Mega2560 with 0021 software.

This arduino should act as a master system for home automation: - time syncronisation from internet - connection to ethernet for confihurring + reading data file from sd card - datalogger temperature and power from salves (jeenodes) - receiving slave messages via RFM12 module - PID thermostat for controlling heating - display infomation on display

So I have the following hardware: - arduino Mega 2560 - new official ethernet/sd shield from arduino (version 2) - RFM12 module connected to mega - LCD display

All works well, but is unstable.

It looks like every time a write to the SD card is done , and the rfm module receive a slave message , the program hangs. Maybe this is only a thought.

I cant't get it stable. I've tried: - all parts + software seperated, it works individually perfect - all parts together and all software (except the code for receiving RF messages): works perfect - as soom as I enable the code to receive RF messages the arduino hangs after 30min-2h.

i've tried disabling interuppts before accesing SD card, but still no improvement.

Now I doubt that it even is possible to get this stable. How should I proceed to debug ?

Can you give some advice, because there are not a lot of experts how have experience with this kind of setup.

Many thanks in advance, Jeroen Meeussen.