GSM Shield Stops Working After While

Hi,

I have an Arduino Uno with GSM Shield that monitor some relays and text me when they change of state.

A couple of months after I implanted the system, the GSM Shield just stoped sending the Texts, i made some tests with the SIM card and the Arduino Uno and they were ok, so i changed the shield and it start working again. I tought that could be some eletric disturb or whatever. But recently happened the same thing, the Shield stoped working again.

I am attaching the code for analysis. Any one could help me discover what i did wrong to damage the shield in long use?

SMS_ARDUINO.ino (4 KB)