I've set up the menus OK, but when I click "Make DVD" it locks up. Also ALL the project properties I set as my new defaults disappear. I tried to run DVD-A in Win. XP compatible mode, but no joy.
DVDA3 is not officially supported in Vista, which means you might be able to get it to work but there's no guarantee. Try asking in the Vista format to see what others may have done to make it work.
Yes, DVDA5 will open DVDA3 projects. Keep in mind that if you save it in DVDA5, you won't be able to open it back in DVDA3 anymore.