Images with captions have padding bug(?) when browser width smaller than image

I first noticed this on my BB Torch, but the same issue exists when resizing a Firefox window on my desktop PC.

I've set up a test webpage with 2 identical images that currently (until fixed!) illustrates the problem.
Only difference is whether a Caption is entered for an image....
http://www.terrencewalters.com/wordpress/test/

Open the link in a separate tab and shrink the browser window below 640 pixels, right down to 300 px.

No caption: padding re-centers with image OK and stays locked at constant padding size around image when browser width is less than image width; body text continues to re-wrap and stay centered

Caption: padding re-centers with image until browser width is less than image width, at which point padding continues to "shrink" with browser window (now padding crops under image)

This really isn't a problem on desktop browsers where the width won't usually be smaller than the width of "smaller" pictures, but it will affect any browser window that is smaller than larger pictures.

Blackberry Torch 9800 screen size is 480x360 px - ideally I'm hoping this glitch can get fixed so that mobile browsing is sweet perfection.

Any suggestions welcome - thx!