Hello.
I have this GSM Shield: http://www.ebay.com/itm/221176159800
gsm shield is working but do not working whit other sensors e.g. dht11 and rain drop sensor. when I plug in this sensors arduino 5V and 3V pins, GSM Shield working faults. Do not reading ip adress.
power DC is 12V, 1000mA or notebook USB port
plz help me. what can I do?
sorry for my bad english.
you should check if the pins that you are using for the sensors are not connected to a reset pin or something from the shield, try to switchs the pins 
Srry for my bad english too !
everything is correctly. but gsm not working. =(