I have been sent the new version of it but not got around to installing yet. My work around was having the DVD as a share and installing from that it then just reads the dvd on first play and is happy.
In Sibelius 5.0, because of the way the shortcut is created, it’s necessary to make some changed for restricted users. I would advise deleting the existing shortcut and making a new one directly from the Sibelius.exe in the Sibelius 5 folder. Copy this to the All Users desktop and try again. Let me know if you still have problems. Incidentally, 5.1 addresses this problem so it might be worth updating. If you are a network version user, I can send you a new LicenceServer for 5.1