This is usually caused by a damaged Sound Preferences file. To resolve the situation, follow these steps:
1. Restart with the Shift key held down to turn the extensions off.
2. Open the Preferences folder (which is in the System Folder) and drag the Sound Preferences file to the Trash.
3. Restart normally.
Mac OS 8.6 can help alleviate this error condition at startup. Mac OS 8.6 is available for download from Apple Software Updates sites.
This article can help you locate the software update mentioned here:
Note: If the removal of the Sound Preferences file does not provide resolution, please troubleshoot for the presence of corrupted fonts.