I'm very sorry that some of you are having problems with VLC after I gave it such a rave review...I have never had any issues, but when I saw some of the replies above I felt a little nervous that I'd passed on some bad advice, so I thought some Googling would be in order... Herewith, a couple of links which may help:
In the second of these, the author does note that:
"Either it may play, or it may seem like it is not doing anything at all.
Don't worry if it doesn't. Wait for a few minutes. As mentioned in the answer in the FAQ above, the player may require some time to decode the stuff or something. Go take a break from your computer. Help yourself to something. Celebrate. You have finally found a way to play all your DVDs on your computer.
After some time, return to your computer and check. Your movie may be waiting for you. If it does not work, sorry. Your celebration was a waste for now. You need to find a different way. Maybe you can get an external DVD drive or something."
I have seen this happen too - sometimes it takes a while for VLC to read the DVD and decrypt it before it starts to play. Maybe as much as 20 - 30 seconds, maybe even longer.
So... Yes, it does look like I was, perhaps, over-optimistic that it could always play everything... sorry about that. But I would say that it may be worth waiting for a while to see whether the player can play the disk after some period of drive access...even if it doesn't leap into life immediately.