I downloaded some MPEG movies from http://www.archive.org and had problems after adding them to Premiere Elements. MPEG-Streamclip (or SUPER) came to the rescue. Here's the story.
After dragging an Mpeg2 file to the timeline, the audio waveform turned flatline at 1 minute and 20 seconds into the movie. This happened with "Zorro (1937)," Chapters 1 and 2, that I downloaded from http://www.archive.org.
VirtualDubMod seemed like the only remedy, but that was going to take 1 hour and 40 minutes to convert. I dumped that and next decided to use Nero to use SmartEncoding to create a quick DVD. That worked very well, but the picture was very dark and needed gamma correction, and the audio was barely audible at the maximum volume on my TV. So I definitely needed to edit this movie.
I finally used MPEG-Streamclip to *demux* the MPEG2 file to separate .MPV and .MPA files. That took about a minute -- a lot better than 1 hour and 40 minutes. I added the .mpv and .mpa files to the timeline in PE and waited for conforming to complete. Happily the audio was all there, and the audio was in sync with the video. I added the Gamma filter to the video and set gamma=7. I then normalized the audio, but adjusted the setting to 12db instead of the 17db. I burned the movie to a DVD using the "western" DVD menu template. I had no problems creating the DVD, and the DVD played back fine on my set-top DVD player.
I've downloaded some other movies from archive.org and have had similar problems with the audio going flatline after about a minute or two. Demuxing the source file into .mpa and .mpv files has always created usable files for Premiere Elements. But in one case the audio was out of sync with the video, as in "Santa Claus Conquers the Martians." The video was about 5 seconds shorter than the audio. All I needed to do was timestretch the video so it's length was the same as the audio.