After updating to 1.3.6, the X server exits whenever some window is created.
Of the built-in styles, this happens only with Makro and MerleyKay, which are the only ones where window.font is a long X font name like "--helvetica-medium-r-normal--12------iso8859-". If the style's window.font is a short name like "lucidasans-10", everything works fine.
confirmed.
fix: http://git.fluxbox.org/fluxbox.git/commit/?id=7b8fd2d81ad80a73564fc9fbb779f47568f12652