ARGGHHHH....Interrupt vector keeps getting called...!!!

I am using the Atmel At91SAM7S-EK with the 256k micro.

I have set up a simple interrupt vector to an ISR which simply acknowledges the interrupt and then exits. However, when the interrupt is entered, it does its business and then exits, to be called again (from the startup.s code) forever after............

Here is the offending code :

void system_int (void) __irq
{        /* System Interrupt Handler */

    AT91S_AIC * pAIC = AT91C_BASE_AIC;
        AT91S_PITC * pPIT = AT91C_BASE_PITC;

    *AT91C_AIC_EOICR = pPIT->PITC_PIVR;     /* Ack & End of Interrupt */
        //*AT91C_AIC_EOICR = 0;                   /* End of Interrupt */
}


void init_timer (void) {                    /* Setup PIT with Interrupt */
  AT91S_AIC * pAIC = AT91C_BASE_AIC;

  *AT91C_PITC_PIMR = AT91C_PITC_PITIEN | AT91C_PITC_PITEN | PIV;                   /* Periodic Interval Value */

/* Setup System Interrupt Mode and Vector with Priority 7 and Enable it */
  pAIC->AIC_SMR[AT91C_ID_SYS] = AT91C_AIC_SRCTYPE_INT_EDGE_TRIGGERED | 7;
  pAIC->AIC_SVR[AT91C_ID_SYS] = (unsigned int) system_int;
  pAIC->AIC_IECR = (1 << AT91C_ID_SYS);
}

Any ideas,
yours completely lost and fed up
Marcus.