Every time you insert a DVD disc that is out of your DVD Drive region, "Drive Region" window will pop-up notifying the "current drive region" and "select new region for drive", which is the region of the DVD disc inserted. And you'll find that Mac the Ripper can't read the disc and all buttons except "Disc" and "Mode" are all grey out.

It's odd that some Mac users do manage to rip DVDs out of their region without changing the drive region. The solution is to disable the DVD player to automatic read and play upon insertion of a DVD movie so that it doesn't ask to change region. I try to disable the Apple DVD Player to start playing disc when a disc is inserted. Nothing happens. I guess they are using different DVD player. Actually, even though they manage to rip the DVDs, the output files are not working normally, missing audio or pictures. Still, not a hanky-dory solution.

Normally, you won't be able to rip DVDs from other regions with MTR without switching the drive region. So you need to change the DVD drive match to the new default region before ripping it. However, you should do it with caution. The DVD drive only allows you to change the region up to 4 times. After making changes four times, the region setting will be fixed to the last region. For example, if you changed the setting to region 1 (USA) at last, the DVD player can play only region 1 DVDs after that.

Note: If you have many DVDs from around the world, you might either to convert your DVD player to not be limited by region with a region-free firmware or buy a portable DVD drive which can be connected to your MBP via USB 2.0 or FireWire, then you can change the setting of the new player another four times.