Xbee S1 packet of instructions

Projects Networking, Protocols, and Devices
2 
    constrain(b1, 0, 255);

Back to the reference page for you. The constrain function returns a value, the constrained value, yet you discard it, making the constrain call useless. Why do you bother?

Is this somehow related to your problem?

  /* //Message new line
  if(comm == true)
  {
    u8g.setPrintPos(0, 46);
    u8g.print('XBEE ON', DEC);  
  }
  else
  {
    u8g.setPrintPos(0, 46);
    u8g.print('ERROR', DEC);
  }
  */

If not, GET RID OF IT!

char inData[10];  // 2 values

Ten is not two in my universe. Are the rules not the same in yours?

if(mySerial.available() > 0);

That ; on the end is the body of the while statement. Hardly seems what you want.