Illustrator changing size of document on export

[ExperimentalM3]

I'm working on an image that is going to be used in a DVD video and as part of the DVD menu. The problem I am running into is that when I export the image as a JPG, Illustrator is resizing the document and I am losing some of the image. I set up the image to 640 by 480 pixels, but when it exports to Jpeg...the size comes out as 572 by 439. Any ideas of what would be causing this? Thanks for your help in advance.

Brian

 

[fizzak]

Is there any white space around the image? Is your artboard @ 640x480? Illustrator will export everything cropped down to the border of the actual art. For example, if you have a 100x100 circle placed in the middle of the artboard and the artboard is 640x480, the subsequent image produced will be 100x100 UNLESS you add a colorless 640x480 box around the art to signify the size you want.