Problem mit PIC-interrupts

//main insterrupt handler

#pragma interruptlow MainISR

void MainISR(void)

{

  Timer1_ISR();

}  

//high ISR routine

#pragma code _HIGH_INTERRUPT_VECTOR = 0x000008

void ISR_high(void)

{

     _asm

       goto MainISR      // Sprung zur Interruptroutine

    _endasm

}  

//low ISR routine

#pragma code _LOW_INTERRUPT_VECTOR = 0x000018

void ISR_low(void)

{

  _asm

       goto MainISR       // Sprung zur Interruptroutine

    _endasm

}

void InitializeRTC(void)

{

  T1CONbits.RD16 = 1;    //16 bit mode

  T1CONbits.T1CKPS1 = 1;  //prescaler: 1:8

  T1CONbits.T1CKPS0 = 1;

  T1CONbits.T1OSCEN = 1;  //enable oscillator circuit

  T1CONbits.TMR1CS = 0;  //use internal clock

  T1CONbits.T1SYNC = 0;  //synchronize timer with external clock

  TMR1L = 0x00;

  TMR1H = 0x00;

  T1CONbits.TMR1ON = 1;  //enable timer 1

}  

void Timer1_ISR(void)

{

  T1CONbits.TMR1ON = 0;  //disable timer 1

  PIR1bits.TMR1IF = 0;  //reset flag

  TMR1L = 0x00;    //reset timer registers

  TMR1H = 0x00;

  MAX7219_DisplayChar(3,'A');

  T1CONbits.TMR1ON = 1;  //enable timer 1

}

//initialize interrupts

void ConfigureInterrupts()

{

  RCONbits.IPEN = 0;    //no interrupt priority

  RCONbits.SBOREN = 0;  //no brownout detection

  //timer

  PIE1bits.TMR1IE = 1;    //enable timer 1 interrupt

  INTCONbits.GIE = 1;      //global interrupt enable

}