VSG:ResetPrefs
Many problems with VLC are due to incorrect settings or a broken plugin cache. You can solve these by deleting VLC's preferences and cache.
Reset preferences from VLC
Using VLC within preferences
If you can launch VLC, in the preferences dialog, from the Tools menu, you can hit the "Reset preferences" button.
NB: This might not solve all your issues, all the time; so if you still have issues, then see the rest of this article.
Reset preferences and cache
Windows
If you installed VLC properly you can delete the preferences and cache by simply opening the shortcut you can find in your start menu:
All programs > VideoLAN > Reset VLC media player preferences and cache files
Deleting the files manually
Open the explorer and type %APPDATA% into the address bar and hit enter. This should lead you to the AppData folder of your user.
Therein you should find a folder named vlc. Delete that folder and you're done.
Mac OS X
Using VLC
In case VLC still launches, open it. Select "VLC" menu -> "Preferences" and hit "Reset All" in the bottom left corner. VLC will ask for confirmation, reset and restart itself.
Manual deletion
First, use a Terminal and enter the following command: defaults delete org.videolan.vlc
Then, remove everything from ~/Library/Preferences called "org.videolan.vlc.*". Use "Go To Folder" within the Finder's "Go" menu to show this folder.
GNU/Linux
Delete the ~/.config/vlc and ~/.cache/vlc folders or execute vlc --reset-config in a terminal.
Old versions of VLC had the data stored in ~/.vlc
BeOS
Delete the config/settings/vlcrc folders.
iOS
Delete the app from SpringBoard and re-download it from the App Store to fully reset the media library and settings.
Android
From the settings
In Settings, go to Applications → VLC → Clear data.
Within the application
Go to Preferences → Other to clean the history and the media database.
