After reinstalling the Sibelius Scorch plugin (and changing the site code to their slightly changed syntax), your sib file appears perfectly in Firefox, but not in Chrome or Safari (both built on the Apple Webkit). Scorch is a 32-bit plugin, so maybe that's causing trouble with the new browsers. I'll keep looking (and trying to figure out what's up with Ville's files not being recognized).
Mac OS: Scorch plugin works on this site in Firefox, not Safari or Chrome
Windows: Scorch plugin works on this site inf Firefox and InternetExploder, not Chrome