Kaffeine cannot play "All Region"

Hi

I have an original "All Region" DVD. When I start to play, it displays the legal warnings, and shows the media company's name, but just after that a message window pops. It says something like;
"xine message
Source is encrypted and cannot be read.
The DVD you use may be encrypted. You may need 'libdvdcss' to use this DVD according to the laws of your country.
(Media stream scrambled/encrypted)"

[Translated]

I'm sure it's not an encrypted, it's just a video DVD. Why doesn't it play? And how can I solve it?

Thanks.