msp430g2553 goes crazy

Hi, everyone!

(I'm completely newbie, so excuse me if my questions are stupid)
I made my first "device" (pic related). It works fine for a short period of time (like an hour or something like that), but then it goes crazy: led start blinking all the time and device don't respond when I change temperature.

Could you please tell me, what's wrong?

 (I tried both - CR3024 battery and 3.3V power supply)

 

#include <msp430.h>
#include <RTCplus.h>

RealTimeClock rtc; //initialise the global RealTimeClock instance

int sensorPin = A3;    // select the input pin for the potentiometer
int ledPin = P1_1;     // select the pin for the LED
int sensorValue = 0;

#ifdef RTCWITHDATE
const char Months[]="JanFebMarAprMayJunJulAugSepOctNovDec";
#endif

void DisplayTime()  //routine to format & print the time to the serial port
{
#ifdef RTCWITHDATE
   const char * MonthText;
#endif
   
   if (rtc.RTC_hr<10) Serial.write('0');
   Serial.print(rtc.RTC_hr);
   Serial.write(':');
   if (rtc.RTC_min<10) Serial.write('0');
   Serial.print(rtc.RTC_min);
   Serial.write(':');
   if (rtc.RTC_sec<10) Serial.write('0');
   Serial.print(rtc.RTC_sec);
#ifdef RTCWITHDATE

   MonthText=Months+(rtc.RTC_month-1)*3;
   
   Serial.write(32);
   if (rtc.RTC_day<10) Serial.write(32);
   Serial.print(rtc.RTC_day);
   Serial.write(32);
   Serial.write(*(MonthText));
   Serial.write(*(MonthText+1));
   Serial.write(*(MonthText+2));
   Serial.write(32);
   Serial.print(rtc.RTC_year);
   
#endif
   Serial.println(" ");
}



void setup()
{
  Serial.begin(9600); //initialise Serial
  
  pinMode(ledPin, OUTPUT);  

  rtc.begin();      //initialise the RTC
  
  rtc.Set_Time(23,59,0); //Set the time to 23:56
#ifdef RTCWITHDATE
  rtc.Set_Date(2013,2,28); //Set the date to 28 Feb 2013
#endif
};

void loop()
{
   DisplayTime();  //call our routine that outputs the time
   
   digitalWrite(ledPin, LOW);
   if (rtc.RTC_min < 5) {
     // CRYSTAL TEST
     //digitalWrite(ledPin, HIGH);
     //delay(25);              
     //digitalWrite(ledPin, LOW);
     //delay(1975);
   } else {
     // THERMISTOR TEST
     sensorValue=analogRead(sensorPin);
     digitalWrite(ledPin, HIGH);   // turn the LED on (HIGH is the voltage level)
     delay(25);              
     digitalWrite(ledPin, LOW);    // turn the LED off by making the voltage LOW
     delay(sensorValue);
   };  
 };


RTC_ISR(void) {
    rtc.Inc();              // Update chunks
 };

(The overall purpose of this device is just to log temperature on SD card)