[SOLVED] Images Displaying Larger than Actual Size in Posts/Pages

Hi,

I've searched for an answer both on the forums and search engines and can't seem to find an answer as to why my images aren't displaying correctly. I don't know what exactly is causing the problem so I thought I'd post here to see if anyone's experienced something similar when posting images.

The Problem:
Photos of different pixel widths are all displayed at the same width in my posts and pages when I select "full size."

For example, I have an image of dimensions 550x413 and one of 600x400 and insert them both at full size into a post. When viewing the post, they are displayed at the same exact size (which is actually larger than the image size itself. If you right click>view image you'll see the size shrink). It seems the images are getting upsized, so to speak.

Atahualpa settings:
Layout max width = 800
Right Sidebar width = 250

I'm not sure where to find out exactly what the center column width is but I believe it's about 650.

I've tried tweaking all of the settings I can think of in both Atahualpa and Wordpress and am at a loss as to what's causing this.

I'm using Atahualpa 3.6.7 and Wordpress 3.2.1. Here's a page with some example images sizes:
http://www.travelswithkim.com/test-image-sizes/

If anyone has any ideas I'd be grateful to hear them.

Thanks so much in advance!
Kim