I would check the operation of the MAX232 chip on an oscilloscope. Make sure the chip is properly stepping the 5 volts up to +10 and to the -10 volts in the charge pumper section. Then check the output of the micro on the TxD pin. This should have nice swing from 0-5 volts. Then compare this signal to that on the output side of the driver on the MAX232 chip. Here you should see the signal swinging from about +9 volts to -9 volts. It should have rise times and fall times that are very short compared to the bit time period. The two signals should appear to be logical inversions of each other, albeit with different voltage levels.

After you look at this come back and describe what you see. We can take the next help step from there.

My gut feel is that for some reason the MAX232 output going to the computer is not swinging with proper voltage levels. This could be any of the problems:
1 - Wiring Error
2 - Max232 not producing +/- 10 volts
3 - Something shorted to the MAX232 output
4 - Bad MAX232 chip.
I would suspect the problem is related in priority order of above list.

Michael Karas