If you want to, you can send us your score and Playback Configuration files (xml file AND data folder) to and we will take a look at it.
Please also let us know which Sibelius version and other instruments you are using and which OS you are working on.
Depending on your OS and Sibelius version, the Sibelius Playback Configurations can be found in one of the following folders:
Windows Vista, Windows 7 and Windows 8: Users\your username\AppData\Roaming\Sibelius Software\Sibelius 6\Playback Configurations or
Users\your username\AppData\Roaming\Avid\Sibelius 7\Playback Configurations
Windows XP: Documents and Settings\your username\Application Data\Sibelius Software\Sibelius 6\Playback Configurations or
Documents and Settings\your username\Application Data\Avid\Sibelius 7\Playback Configurations
Mac OS X: Users/your username/Library/Application Support/Sibelius Software/Sibelius 6/Playback Configurations or
Users/your username/Library/Application Support/Avid/Sibelius 7/Playback Configurations
Best regards,
Andi