I was trying to use the latest Pencil (version 2.0.3) in Ubuntu 12.04, but the PNG exporting does not work, with Pencil working both inside and outside Firefox (which is 19.0.2).
The export page as PNG dialog asks for where to put the file but fails silently after that, and the export document using any HTML template gets you this dialog stalled forever:
How can I fix it?