Arduino won't upload

spcomputing:
Have you tried CodingBadly's loopback test?

http://arduino.cc/forum/index.php/topic,73748.0.html

I just tried it, and it failed the test. The RX LED flashes when I send something, but the TX doesn't, so I get nothing back.
(by serial monitor he did mean the thing that pops up when I press CTRL+SHIFT+M in the Programming environment, right?)