I have the Arduino Duemilanove with the 328 chip. Everything was working great, I got the blinking program to run, and I added two LED w/built in resistors and I had them blinking back and forth, but all of sudden I could not upload anymore programs. The COM port went away, but the lights still keep flashing back and forth. Would anyone have any idea on how to fix this problem? This happened in Windows XP 32bit, and it did not work either on Windows Vista 64bit either. 
-Thanks.
Correction the COM did not go away, however I tried installing the correct drivers and Windows will not let me, it says it already has the correct ones installed but I get this error from the compiler (IDE 0015)
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51
Did you try the troubleshooting guide? http://www.arduino.cc/en/Guide/Troubleshooting#upload
avrdude error problems are not infrequent and seem to occur for many reasons; although definitive reason(s):solution(s) have, to my knowledge, not been found.
You might want to look at this thread for my experiences:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1233093517/39#39
Hope this helps.
/david
I know the problem now, I am using pin 1 here, and I thought since I know the problem, I should start another thread.
I just got started and I found that I had to recheck my board identification in build 015 of the arduino software. For some
strange reason it was identifying a different board with an 8 Mhz
clock crystal. as soon as I selected the other board my
AVRDUDE errors went away and the blink program downloaded
normally. 