Thanks to Kris Schultz and Rory Francis for sending me some screenshots of the display from Mac IE 5.
The problems were with the menu, which formerly used a display of "inline-block" on the anchor elements. And the forms needed some tweaking.
To fix the menu, I simply removed the "inline-block." For the forms, I simply had forgotten to implement a fix that Mark Newhouse helped me come up with for my CSS Forms a few weeks ago.
The site still has some display issues with IE 5 PC, but I really am not too worried about them. The point of this site is not to visually "wow" everyone.