Digitalbits.com reports that:
While we're on the subject of the Star Wars DVDs, we've been getting many, many questions and complaints about the audio changes and "music issues" on A New Hope. All we can tell you is that Lucasfilm claims the audio on the disc is exactly as they intended it to be. HOWEVER, we are also getting a lot of complaints from readers who have been experiencing a disc playback problem with A New Hope. Apparently, on many players, the disc freezes for a few seconds (we suspect near the layer switch point) and then skips ahead several minutes. Fox Customer Service is taking the names and addresses of people who are experiencing this problem so they can arrange to send you a fixed replacement disc. You can call them at 888-223-2FOX. Again, this addresses the freezing problem only. This is not a replacement for any sound issues. Just FYI.
Hope this is helpful to people. I'm considering doing it myself as I've noticed some odd glitches on my disc (I just assumed it was a PowerDVD issue, now I'm convinced it's not just me).
In a somewhat related vein, here's an chat transcript with the guy responsible for the DVD set: