This may be a bad idea. Things might go from bad to worse.
You can try doing a sudo apt-get purge libqt*
It will ask you to confirm packages to remove under 'The following packages will be REMOVED:'. Copy those packages in a text file somewhere because we will re-install them again. Confirm and remove them.
Next run a sudo apt-get clean
and sudo apt-get autoremove
.
Then go to your /home/.config folder and delete the vlc folder in there.
Then reinstall the core packages like ubuntu-desktop, totem and vlc and see whether it will work this time.
I tried this (I didn't confirm though) and the packages that were to be removed included: unity-2d, vlc, skype, qbittorrent, totem, ubuntu-desktop, speedcrunch and alot of qt plugins.