WordPress test data Resized and Twenty Ten theme?

Hi guys,
I have created a theme to submit using the twenty ten styles as a basis.

One of the test data tests is a wide image resized, this does not work in the default twenty ten theme, I have tested this with my theme and twenty ten as well and the images are not correct in the sample data test:

Centered Image with Caption, this spills into the sidebars.
Image is 900x598px, resized in editor to 329×222 ignores the resize.

I have narrowed it down to this style block which seems to over-ride the width and height.

#content img {
	margin: 0;
	height: auto;
	max-width: 640px;
	width: auto;
}

If I remove the height and width auto settings it corrects the test data image list display.

#content img {
         margin: 0;
	max-width: 640px;
}

I have already submitted the revised theme without the image style change, but this is bugging me!

Anyone know if there is any other knock on effect with other browsers if I remove the width and height auto settings?

Here is the corrected theme!

David