Having tried the troubleshooting options in http://www.arduino.cc/en/Guide/Troubleshooting#upload, I'll describe the problem here.
***Your operating system: Windows XP SP2
***What kind of board you have. If it's a Mini, LilyPad or other board that requires extra wiring, include a photo of your circuit, if possible.
Arduino Diecimila
***Whether or not you were ever able to upload to the board. If so, what were you doing with the board before / when it stopped working, and what software have you recently added or removed from your computer?
- Connected Arduino via USB, was successful with Blink demo.
- Connected Arduino LCD-shield V1.1 (www.nuelectronics.com), was successful with LCD4Bit_mod example (a test of LCD shield buttons).
- Uploaded my own first LCD-shield sketch.
Now the LED (pin 13) blinks rapidly continuously and even with the LCD shield disconnected, I cannot upload any sketch to the Arduino.
***The messages displayed when you try to upload with verbose output enabled.
This is what displays when I try to upload the Blink sketch:
Binary sketch size: 1096 bytes (of a 14336 byte maximum)
C:\Program Files\Arduino\hardware/tools/avr/bin/avrdude -CC:\Program Files\Arduino\hardware/tools/avr/etc/avrdude.conf -v -v -v -v -pm168 -cstk500v1 -P\.\COM4 -b19200 -D -Uflash:w:C:\Program Files\Arduino\examples\Digital\Blink\applet\Blink.hex:i
avrdude: Version 5.4-arduino, compiled on Oct 11 2007 at 19:12:32
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
System wide configuration file is "C:\Program Files\Arduino\hardware/tools/avr/etc/avrdude.conf"
Using Port : \.\COM4
Using Programmer : stk500v1
Overriding Baud Rate : 19200
avrdude: ser_open(): setting dtr
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Recv:
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: Send: Q [51] [20]
avrdude: Recv:
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51
avrdude done. Thank you.