The recently-updated xemacs packages (21.1.14-2.62) have Info-directory-path set incorrectly. I don't have the full value available, but the path contains something like "/usr/lib/xemacs/xemacs-packages/info/" "/usr/share/info" Rather unfortunately, the latter directory doesn't exist on a stock RH6.2 system. Bringing up info breaks with a fatal error as a result.
Doh. We tested for other changes (like aspell vs. ispell), but not this. Workaround: Edit /usr/share/xemacs-21.1.14/lisp/site-start.el , and change the infopath to point at /usr/info instead of /usr/share/info. This is not a problem with current releases, as they actually have the info pages in the FHS-compliant location.