I agree with San. You have delays in your interrupt that cause your interrupt to take longer to execute than it takes to receive the next character.

Generally, Serial Receive Interrupts grab the data as fast as possible, store it somewhere, and immediately return. Your program can then manipulate the data received somewhere else, perhaps in "MAIN".

Be sure to check how fast your unit will be receiving data compared to how fast your "MAIN" routine can write it to the LCD. You may need to implement some kind of FIFO buffer that will allow your code to buffer characters that are received by the program while it is still busy writing to the LCD.

If the sustained receive rate is higher than the maximum speed you can write to the LCD, you may have a problem--or may need to implement some kind of handshaking so that your receiving unit can signal the sending unit to stop sending data until the receiver writes everything it can to the LCD.

Good luck,
Craig Steiner