Hi Richard,
I have not read all the above posts, but I can share some of my troubleshooting methods:

1. Short the TxD,RxD pins at the back of the PC on the COMx Port.
Try the method of HyperTerminal. I suppose you have already tried this method, and it works OK.

2. Switch OFF the power to your Board, Remove the MAX232 from your board, Short the 2 Pins of MAX232 Socket that are connected to the connector that goes to the PC. Now Power ON the Supply to the Board. Check with the HyperTerminal again. If it does not work properly, then there is definitely some problem in the cable, or in Ground Connections, or Power to the Board. Then it MAY NOT be a problem of MAX232.

3. In the above step if you get correct results, then your cable is OK. Now Switch OFF the power to the Board. Remove the shorting you placed on the MAX232 Socket. Place the Max232 in the Socket, remove the CPU from the board, and short the MAX232 driver Input/Output Pins that goes to the CPU Pin 10,11. Please note, you have to short them at the MAX232 Socket. There is a difference in placing a short at the MAX232 socket and shorting the CPU Socket pins 10,11. Don't forget the PCB track is inbetween the MAX232 Socket, and the CPU Pin10,11. Now again check it with the HyperTerminal. If it gives you problems, then there is definitely a problem in MAX232 and its related circuit. In this case you NEED a Scope to solve the problem as suggested by many members in this thread. Check the Pullup Resistors that are placed on CPU Pin10,11, or even the RPack that is generally used for pull up.

Mr. Kiran V. Sutar