As stated in the title, I can't play any commercial DVD on my internal DVD-drive on my laptop, but everything works just fine for the same DVD played on an external (USB) DVD-drive.
I've installed ubuntu-restricted-extras and used the usual script: sudo /usr/share/doc/libdvdread4/install-css.sh
I might add that this problem is encountered on 3 different laptops, so it's not a physical problems on my machines (hopefully ;)).
Thanks to anyone who would have a solution... :)