resetting or loading new sketch

I'm new to the Arduino and I tried my first project today. I uploaded the script "Blink" to my Arduino Uno and worked instantly. I then tried to change the duration of the blink, and I can't seem to load the new code in. I tried closing the old sketch box, re-opening it, renaming it, and everything I could think of. The Uno runs the first script continuously, and I can't reset with the button. I tried pressing the reset on the Uno with the usb cable connected, then unplugging and re-plugging, and all kinds of other ways to reset. When I try to load a new sketch, the info bar at the bottom of the sketch window says "Uploading..." for a while then stalls with the green status bar nearly filled, and eventually gives a message "Problem uploading to board" Wow -rb

Go to Preferences and and check the box for "Show verbose output during: [ ] compilation [X] upload". Try the upload again and if the meaning of the messages is not clear, report them here and maybe someone can tell you why it is failing.