prettyPhoto: expanded image being cut off

Once I click on a thumbnail on a portfolio page and the full image is shown, when I click on the expand button to see the full, unscaled image (which is now larger than my screen resolution), the left side of the view window is off the left side of the screen. Even though the scroll bars appear along the bottom and right sides to allow me to move the parts that are off screen into view, the scroll bar along the bottom, though scrolled as far left as possible, does not bring the left side of the image into view. The scroll bars allow me to see the top, bottom, and right extents of the image, but not the left.

Any ideas? Is there a maximum size setting for the view window, and if I exceed that, it truncates a portion of the image on the left side?