A likely cause is the hard drive’s inability to read the audio in a timely fashion. Possible causes…using one hard drive for source and preview files and conformed audio. Also badly fragmented drives will frustrate the reading abilkity of the drive. Nearly full (over 80%) drives get very slow.
What is your system configuration?
Best bet is to play the DVD from a stand alone player while capturing it in Premiere, using your camera as a analog/digital passthru or use an A/D converter.
Premiere Pro is really not good at editing already compressed files, especially Mpeg. Your preview problem is common. Suggest rendering previews (Enter) first if you plan to do more than just cut the stuff up.