Apple has confirmed that there is a problem with reading some of the dual layer DVDs on the Matsushita DVD drives that are installed in many of their computers. We are waiting to hear back from them. As a temporary solution we have set up a web page where you can download either the installer or the whole installer disk image. Please paste this link into your browser's URL window. It will take you to our Sibelius 6 download page. All the necessary files and the installation instructions are on that page.

http://www.sibelius.com/helpcenter/updates/sib6_0_download.html

The alternative solution would be to mount the installer disk on another Mac and install over the network or copy the installation files onto a removable disk.