Arduino Reboots it self when it receives a text message it has to process

I have tried powering the arduino and shield via USB and an external 2A Powersupply, nothing helps.

First off, i forgot to mention, i am using the GSMSHIELD library.

It has 4 sms commands it should respond to As listed below:

VP - Poweres on the heater manually, by activating the function varme() which turns on the relay for the heater.

15 - a setting set for 15 degrees, starts and stops the heater accordingly. Again by activating the function varme().

22 - same as above, just with 22.

Status - Responds a status message, which contains information about the current temperature (Temperaturen er lige nu = The temperature right now) and wether or not a temperature controller is active (the function 15 or 22).ยจ

When ever it receive a text, it shows this in my serial connection:

RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: 
+CMGL:
ATT: OK
RIC: 
+CMGL: 1,"REC READ","+4522234850","","14/04/23,20:4
ATT: OK
RIC: 
+CMGL: 1,"REC READ","+4522234850","","14/04/23,20:44:37+08"
Vp

OK

ATT: +CMGL:
RIC: 
+CMGL: 1,"REC READ","+4522234850","","14/04/23,20:44:37+08"
Vp

OK

And then it reboots.

While not receiving a message, it shows this:

ATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: 
OK

ATT: +CMGL:
RIC: 
OK

If it receives a text it does not have to respond to, it stops, and does nothing, as shown below:

ATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: NO STRING RCVDATT: OK
RIC: 
+CMGL: 1,"REC UNREAD","+4522234850",
ATT: OK
RIC: 
+CMGL: 1,"REC UNREAD","+4522234850","","14/04/23,21:11:00+08"
Bum

OK

ATT: +CMGL:
RIC: 
+CMGL: 1,"REC UNREAD","+4522234850","","14/04/23,21:11:00+08"
Bum

OK