LPC23xx, GCC and UART0 ISR not responding

 VICSoftInt = 0x40;

/* Constants to setup and access the UART. */

#define serDLAB              ( ( unsigned char ) 0x80 )

#define serENABLE_INTERRUPTS      ( ( unsigned char ) 0x03 )

#define serNO_PARITY          ( ( unsigned char ) 0x00 )

#define ser1_STOP_BIT          ( ( unsigned char ) 0x00 )

#define ser8_BIT_CHARS          ( ( unsigned char ) 0x03 )

#define serFIFO_ON            ( ( unsigned char ) 0x01 )

#define serCLEAR_FIFO          ( ( unsigned char ) 0x06 )

#define serWANTED_CLOCK_SCALING      ( ( unsigned long ) 16 )

/* Constants to setup and access the VIC. */

#define serUART0_VIC_CHANNEL      ( ( unsigned long ) 0x0006 )

#define serUART0_VIC_CHANNEL_BIT    ( ( unsigned long ) 0x0040 )

#define serUART0_VIC_ENABLE        ( ( unsigned long ) 0x0020 )

void init()

{

.............

      /* Setup the baud rate:  Calculate the divisor value. */

            ulWantedClock = ulWantedBaud * serWANTED_CLOCK_SCALING * 4;  // * 4 because of PCLK_UART0

      ulDivisor = configCPU_CLOCK_HZ / ulWantedClock;

      /* Set the DLAB bit so we can access the divisor. */

      U0LCR |= serDLAB;

      /* Setup the divisor. */

      U0DLL = ( unsigned char ) ( ulDivisor & ( unsigned long ) 0xff );

      ulDivisor >>= 8;

      U0DLM = ( unsigned char ) ( ulDivisor & ( unsigned long ) 0xff );

      /* Turn on the FIFO's and clear the buffers. */

      U0FCR = ( serFIFO_ON | serCLEAR_FIFO );

      /* Setup transmission format. */

      U0LCR = serNO_PARITY | ser1_STOP_BIT | ser8_BIT_CHARS;

      /* Enable UART0 interrupts. */

      U0IER = serENABLE_INTERRUPTS; //RBR and THR IRQ

      /* initialize VIC */

      VICIntEnClr  = 0xffffffff;

      VICVectAddr  = 0x00000000;

      VICIntSelect = 0x00000000; /* all IRQ */

      /* Setup the VIC for the UART. */

      VICIntSelect &= ~( serUART0_VIC_CHANNEL_BIT ); //IRQ, not FIQ

      VICIntEnClr = serUART0_VIC_CHANNEL_BIT;

      VICVectAddr6 = ( long ) vUART_ISR_Handler;

      VICVectCntl6 = 0xF; //Prio

      VICIntEnable |= serUART0_VIC_CHANNEL_BIT;

..........

}