Electronic – interrupt using Timer0 on PIC18f

Im looking for a little help and advice on my code.

Im using C18 in the MPLab environment, PIC18f4520 with Fosc @ 4MHz, and usnig timer0 in 16 bit mode to count to overflow, set the overflow bit and interrupt flag, then jump to ISR and increment a variable 'count'. This is outputted to a port with LEDs attached so that I can get visualy confirmation of the program working.

However, the outputted count is always '1' (i.e. 0x01) and I believe that the ISR is only happening once, if at all.

Any help that you can offer would be most appreciated.

Here is my code:

void main (void)        /*                                                                                      */
{                   
TRISA = 0;          /*                                                                                      */
TRISC = 0;          /*                                                                                      */
TRISB = 0;
TRISD = 0x00;
RTOS();
}
void low_interrupt (void)
    {
    _asm GOTO timer_isr _endasm
    }
    #pragma code
    #pragma interruptlow timer_isr 

void timer_isr (void)
    {
    INTCONbits.TMR0IF = 0;
    count = count++;
    LATD = count;
    RTOS();
    }
void RTOS (void)
    {
    T0CONbits.T08BIT = 0;   // 16-bit timer
    T0CONbits.T0CS = 0;     // increment on instruction cycle input
    T0CONbits.T0SE = 0;     // increment on low--> high transition of clock
    T0CONbits.PSA = 1;      // T0 prescaler not assigned i.e. 1:1 prescaler.
    RCONbits.IPEN       = 1;    //Enable Interrupt Priorities
    INTCONbits.GIEL     = 1;    //Enable Low Priority Interrupt
    INTCONbits.GIE      = 1;    //Enable Global Interrupts            
    INTCONbits.TMR0IE   = 1;    //Enable Timer0 Interrupt
    INTCON2bits.TMR0IP  = 0;    //TMR0 set to Low Priority Interrupt
    INTCONbits.TMR0IF = 0;  // T0 int flag bit cleared before starting
    T0CONbits.TMR0ON = 1;   // timer0 START
    while (1);
    }

Thanks in advance for any guidance you can offer.