Lpc2000

I have the following problem that is very odd.

I have a very simple program that waits one char from the uart0 and 
sends it back to it.
If I set the baudrate to 57600, it works ok, but if I set the baud rate 
to 115200, the host (PC)  understands any data I send, but the LPC just 
gives Frame errors even if a single byte is sent.....
I'm using a LPC2146 @ 12Mhz
Using these constants in the baud rate generator should give an error of 
0,16%, and the transmission works... Why can't I receive data ?
Thanks, Mauricio


This is the code:

void ser0_init(void)
{
  U0IER = 0;
  U0IIR;
  U0RBR;
  U0LSR;

  U0LCR    = 0x83; // Enable access to divisor latchs

// 57600 @ PERCLK = 12Mhz
//  U0DLL    = 13;
//  U0DLM    = 0;
//  U0FDR    = 1<<4|0; // MulVal[7..4]  DivAddVal[3..0]

// 115200 @ PERCLK = 12Mhz
  U0DLL    = 1;
  U0DLM    = 0;
  U0FDR    = 2<<4|11; // MulVal[7..4]  DivAddVal[3..0]

  U0LCR    = 0x03;  // 8n1
  U0FCR    = 0x87;  // FIFO enabled and cleared; Trigger @ 8 bytes
}

unsigned char ser0_getc (void)
{
  while (!(U0LSR&0x01));  // RDR
  return U0RBR;
}

void ser0_putc(unsigned char ch)
{
  while (!(U0LSR&0x20));  // THRE
  U0THR = ch;
}

int main(void)
{
  Initialize();
  ser0_init();

  ser0_putc('O');
  ser0_putc('k');
  ser0_putc(0x0d);
  ser0_putc(0x0a);
  while (1)
    {
      ser0_putc(ser0_getc());
    }
}