I found the problem. One of my guest writers inserted some funky encoding stuff (probably copy and pasted from a word document?) that buggered the rest of the site.
I now need to ask how she did that. =\
Thanks for the advice. I see the same behavior using the default theme, so I don’t believe that is it (I switched back to the default theme this morning again to see… nadda). I *was* using this theme successfully for a few months with both browsers being supported just as well.