hi,
you have not specigied OSC frequence.
But looking on your code, I make some sonclusions:
- you use 11059200Hz OSC freq.;
- you use 2400 baud rate.
If my idea is correct then I think that the problem on PC side:

First of all, look about how you set COM-port baud rate in case 1 and case 2:

case 1:
outportb(0x3f9,0x0c); //Put in divisor MSB 30h 
outportb(0x3f8,0x00); //Put in divisor LSB 00h

case 2:
outportb(0x2f9,0x30); //Put in divisor MSB 30h 
outportb(0x2f8,0x00); //Put in divisor LSB 00h

In case 1, you commented MSB 30h but in program it is 0x0c.

Anyway, it is just a mistake. The main error is that for 2400 it must be vice versa:

outportb(0x2f9,0x00); //Put in divisor MSB 0 
outportb(0x2f8,0x30); //Put in divisor LSB 48

i.e. frequence divider must be 48, not 12288. Otherwise COM port uses baud rate about 9 bits per second. As result, UART of C52 (configured to 2400) detects start bit and then reads 8 bits as zero because COM port is too slow. PC even does not start data transmit at time when UART has already read all data. So you get 0x00.

Regards,
Oleg