I had transcribed subtitles from a video of a degraded print with subtitles on the print itself (quite eye-straining in some scenes with white background) and was able to sync them up to a better version. I noticed a subtitle I missed and I wanted to change the font to something bigger (I used Arial Narrow). When I opened the .srt file that I muxed with the video and audio in DVDAuthorGUI, I found the timings were off from the timings on my final DVD itself. For instance, one line that should occur at 58:37 according to the subs occurs 2 seconds later on the film (in sync). I then ripped the subs from the DVD with VSRip and converted it to a new .srt with SubResync and found the timings to be identical to the original .srt. There are no problems with the sync on the final DVD. How accurate is PowerDVD's timing? This is what I used to look at the film to check the time against the subtitle file. Since the timing of the ripped file is the same, I don't think something happened during the multiplexing to add two seconds to my video/audio/subtitles.