VLC: aspect ratio wrong & no colour
I have two machines running Debian Squeeze. On the one machine VLC works perfectly in that it displays video files in colour and with the correct aspect ratio. On the other machine the images are all b&w and have a portrait, instead of landscape, layout. The image has a ratio of, roughly, 1:4.
I've compared the files that I have installed for codecs and vlc and everything that's on the machine with the functioning VLC is also on the other machine.
I've already uninstalled and reinstalled VLC. No luck.
Totem Movie Player, Gnome Mplayer and xine all function correctly on the machine where VLC does not.
Can anybody suggest something that I can check, change, etc? If I have to provide more info, I'd be happy to do so.
PS: The reason why I want to get VLC working is to view iso files before burning it to DVD.