Arduino code not working
Please format your code.  I know it takes longer, but the payoff is in readability and maintainability.  It's well worth the extra effort.

LiquidCrystal lcd = LiquidCrystal(12, 11, 5, 4, 3, 2);

const int sensorPin = A0;
int switchState = 0;

double Thermistor(int RawADC)
{
    double Temp;
    Temp = log(((10240000 / RawADC) - 10000));
    Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp)) * Temp);
    Temp = Temp - 273.15;
    return Temp;
}

void setup()
{
    Serial.begin(9600);
    lcd.begin(16, 2);
    pinMode(sensorPin, INPUT);
}

void loop()
{
    switchState = digitalRead(sensorPin);
    int readVal = analogRead(sensorPin);
    double temp = Thermistor(readVal);
    Serial.print("Temp. : ");
    Serial.print(temp);
    Serial.println(" Celsius");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Temp: ");
    lcd.print(temp);
    lcd.print(" C");
    delay(500);
}


I think the problem is the

lcd.print(temp);


Try casting it to a float from a double (and two decimal places).  Maybe you just need the decimal places.

lcd.print((float)temp, 2);