Open Library. Note The Library folder is hidden in MAC OS X Lion. To display this folder, hold down the OPTION key while you click the Go menu.
Drag all files that use this name structure to the desktop:
com.microsoft.outlook.xxx.plist (where xxx is a placeholder for a name) Example file: com.microsoft.outlook.database_daemon.plist
Start Outlook to see whether the issue is resolved.
inaccessible not visible gone disappeared clicking nothing happens