I'm having this problem since about 2 releases and hoped that you can fix it with 2.2.1
But after installing the version today the error is still there.
Same problem here. After installing vlc and making it the default player, all previews disapeared.
When you set windows media player as default all the previews are back again.
After installing the vlc 2.0 version i found out, that there is no context menu in the windows explorer for the vlc-player.
I then deinstalled and installed it new again, but the problems stays, allthough the option is set in the installation menu.