If you backed them up on your hard disk, then the only player I've found easy to do this is Kaffeine, where you can load a directory and change the subs and choose menu.
I see you are using Ubuntu, I won't tell you to install kde but VLC is a very very good player which I think can do this work for you.
For installation help check here
Hope this helps
EDIT: Oops! I just realised that above you metnioned you are making a copy of the dvd to another dvd-r and not in the hard disk. Have tried to write to maybe a dvd+r and see if it works? Or maybe another brand of dvd-r's. Try copying the disks on a slower speed, or even not on the fly.
Also please post the last lines of the command dmesg after the lock-up of the drive happens.