Clearing Preferences and Databases for Pro Tools 10 on Mac OS Lion.
Trashing the temporary preference and database file is an easy way to “reset” Pro Tools without losing important things like session files, or having to reinstall. Follow the steps below carefully, making sure you complete each step.
Quit all applications and verify that the Finder menu is at the top of your screen (next to the Apple menu).
While holding the OPTION key, click the GO menu and select Library.
Inside this Library, locate and double-click Preferences. Inside this Preferences folder, locate the following items and drag them to the Trash:
DAE Prefs (folder)
Pro Tools Preferences.
Close all windows and open the Macintosh HD. Navigate to Library > Application Support > Avid > Pro Tools > Databases > Unicode > Volumes.
Drag the contents of the Volumes folder to the Trash (there may be a few or several with odd names).
Restart your Mac and empty the Trash. Launch Pro Tools. Be sure to visit Setup menu > Playback Engine and choose your hardware as the current engine.