Antonio Rojas, the Arch Linux TeXmacs packager, figured out that I needed to override the default QT style for my environment with QT_STYLE_OVERRIDE=windows. I found that "Cleanlooks" also worked and looked a little better to me. He hadn't noticed the crashes since he was using KDE. Now I can see the color palettes and insert symbols without crashes. It seems there is a problem when QT thinks the default style should emulate GTK.