I had this problem a couple of years ago. This seems to only affect MP4 files. If you convert the MP4 files to Real Media HD then they will burn without problem. (Right click on the video file in your library, then right click on EDIT, then click on CONVERT, selecting Real Media HD). This does take a bit longer to do, as it does take time to convert the files, and I found sometimes a low light or fast moving scene will pixel slightly, but at least you will be able to burn discs again.
It is worth noting that my - error parsing ac3 audio stream - problem was eventually fixed by Real Player support connecting to my computer and downloading - k-lite codec pack - which solved the problem completely for me, I was apparently missing some software for audio and video playback.