I've never had this much trouble before, most of my DVDs simply wouldn't play at all. I installed tons of libraries, cleaned scratches, nothing... And no error messages from any of several programs gave me a clue as to the problem.
Finally I found a post mentioning having no region set on a DVD drive. I found and downloaded "regionset" and sure enough that did the freaking trick.
~ $ regionset /dev/sr0
Current drive parameters for /dev/sr0:
RPC Type: Phase II (Hardware)
RPC Status: no region code set (bitmask=0xFF)
Vendor may reset the RPC 4 times
User is allowed change the region setting 5 times
Would you like to change the region setting for this drive? [y/n]: y
Enter the new region number for your drive [1..8]: 1
New RPC bitmask is 0xFE, ok? [y/n]: y
Region code set successfully.
After which everything played just peachy.
