You are trying to debug many things at once, and that is a recipe for making things difficult.
Please use a single computer (I suggest one of the Macs– generally a little more forgiving), and start with a fresh copy of the Arduino IDE. Try to upload the “blink” example sketch to your Uno, and make sure that it works.
To make sure that it’s actually uploading code successfully, try changing the “delay(1000);” lines to read “delay(250);”.
Then, with the _exact same setup_ — same computer, same USB cable, same copy of Arduino and so forth — try uploading to your duemilanove. The only thing that you should need to change is the selection in the Boards menu.
