The initial Firefox 3.0 release behaves exactly the same, so likely the default SVG-only icon theme on Ubuntu 9.10 just exposed for the first time some issues or of moz-icon:// protocol.
Actually, it is enough to change the filename extension of SVG icons from .svg to .png (e.g. put symlinks into ~/.icons/Humanity/mimes/$ICON_SIZE/ with .png as extension) to make them "work".
The initial Firefox 3.0 release behaves exactly the same, so likely the default SVG-only icon theme on Ubuntu 9.10 just exposed for the first time some issues or of moz-icon:// protocol.
Actually, it is enough to change the filename extension of SVG icons from .svg to .png (e.g. put symlinks into ~/.icons/ Humanity/ mimes/$ ICON_SIZE/ with .png as extension) to make them "work".