This is what I got. Just changed background image from this theme and put 1680 and 1050 in screen_width and screen_height and boot_height and boot_width.
Okay, so we now know that Chameleon is not using 1680x1050.
Find out what resolutions are available to Chameleon. To do that, you need to boot in to the Chameleon GUI, press the down arrow on your keyboard to bring up the menu. Then down arrow to the sixth option 'Video Info' and have a look in the resulting list to see if your desired resolution is there.
If it's not, then it can't use that resolution on your hardware then you need to find the next best option whilst keeping with a resolution that's also in keeping with your screens aspect ratio. In my
Resizing Themes guide, I have linked to an image from wikipaedia to help identify resolutions.
EDIT: I am guessing Chameleon is using 1366x768 on your system.....