I2C is different between MEGA and UNO?

One of the device is http://www.geekonfire.com/wiki/index.php?title=I2C_OLED_Panel(128x64)#Resources. It works on UNO and MEGA at 100kbps, but at 400kbps only works at MEGA.(I have tested it on MEGA2560,MEGA1280 and MEGA Olympic)

code in library:
//uint8_t twbrbackup = TWBR;
//TWBR = 12; // upgrade to 400KHz!
// TWBR = twbrbackup;
if I enable the above sentences, It doesn't work at UNO.

void GOFi2cOLED::display(void) {
  sendCommand(0x00 | 0x0);  // low col = 0
  sendCommand(0x10 | 0x0);  // hi col = 0
  sendCommand(0x40 | 0x0); // line #0

    // save I2C bitrate
    //uint8_t twbrbackup = TWBR;
    //TWBR = 12; // upgrade to 400KHz!

    // I2C
    #if defined(ARDUINO) && ARDUINO >= 100
    for (uint16_t i=0; i<(128*64/8); i++) 
    {
      // send a bunch of data in one xmission
      Wire.beginTransmission(SlaveAddress);
      Wire.write(GOFi2cOLED_Data_Mode);            // data mode
      for (uint8_t x=0; x<16; x++) 
      {
        Wire.write(buffer[i]);
        i++;
      }
      i--;
      Wire.endTransmission();
    }      
    #else
    for (uint16_t i=0; i<(128*64/8); i++) 
    {
      // send a bunch of data in one xmission
      Wire.beginTransmission(SlaveAddress);
      Wire.send(GOFi2cOLED_Data_Mode);            // data mode
      for (uint8_t x=0; x<16; x++) 
      {
        Wire.send(buffer[i]);
        i++;
      }  
      i--;
      Wire.endTransmission();
    }
    #endif    
//    TWBR = twbrbackup;
}