Just a quick note to let you guys know that we’re looking into an issue where an “Unable to open External Preview” alert is shown, after exporting a page with a PHP extension. This is due to a change in OS X, and we’re investigating. Right now, the only workaround I can suggest would be to disable this option in RapidWeaver’s preferences.
I’ll keep you guys in the loop as our investigation progresses. We’re currently investigating this as part of our work on 6.3.1, but this is subject to change depending on the scope / nature of the bug.