I'm not sure if it's related but try placing a delay between entering the PIN and attaching gprs. Don't try to do them together as I found out here:http://forum.arduino.cc/index.php?topic=173860.0As for your second question, by press and holding the button for a couple of seconds, you turn off/on the shield
They should solve this issue.
if((gsmAccess.begin(PINNUMBER, false)==GSM_READY) &
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