GBoard GSM and SD problems

I am using the GBoard (http://imall.iteadstudio.com/development-platform/arduino/arduino-compatible-mainboard/im120411004.html) as the master communicator for a project of mine. What I am trying to do is receive information via the Xbee, save it to SD card, and then send it via GSM to a server of mine. Communication with the GSM module is done via software serial and hardware serial for the Xbee. I am using the GSM_Shield library for the GSM and SdFat for the SD. Currently, I have been able to get the GSM, SD card, and Xbee working separately, but once I combine the code for the GSM and SD in a sketch things start breaking. Has anyone used all three GSM, Xbee, and SD modules on a Gboard at the same time? If so, how did you go about doing it?

but once I combine the code for the GSM and SD in a sketch things start breaking.

How much free memory do you have left?