Hi,
1) Start by getting your serial comms working without interrupt. Then add the interrupt capabillity later.
Code:
INIT:
   HSEROUT["Program Start",10,13]

Main:
   HSERIN[Char] 
   LCDOUT $FE,1,"DATA: ", Char
   HSEROUT[Char]
   TOGGLE LED
GOTO Main
2) My guess would be that PUTTY is set so that it displays what the device echos back and not what you type locally and since your device isn't currently echoing what you type you don't get anything in window (many serial terminals work this way by the way). Check the documentation for PUTTY.

Finally, please use the code tags when posting code - here's how to do it.

/Henrik.