Since you use includes with your pages, is it possible to provide a link to swap out the dual-column layout for a single column layout? Similar to the break out of frames concept.

Are there any other accessibility problems this student indicated?

Heh, very timely and interesting Farron - especially since I enlarge text quite often too. Sometimes as high as 150% or 200% in Opera's zoom; due to the fact that I'm at 1600x1200. Since Opera is my default, I don't really find it causes me big problems.
As to the style-swapper idea: I think you've got a point there. Most people do this more for visual flair/colours ... but actually functionality would have to rate higher than aesthetics here!
Should be possible to do an alternative stylesheet which maybe has the nav/links from the sidebar instead both rendered at the top and bottom of the page.

As to JS-disabled: Surely there's a solution for style-swapping that does not require JS ...? I'm sure I've seen something somewhere (but don't ask me where!).

For those who can't quite visualize or replicate the problem - I have posted two screenshots here:
http://jaenus.pinkbat.com/lvsblogging/Opera-largefont-sidebar.png
http://jaenus.pinkbat.com/lvsblogging/Opera-FF-largefont.png