Playback problem - video playback stops; any suggestions?

Question

I have distributed about 20 copies of a DVD I made using iMovie and iDVD v4.x - and about 5 of the discs are reported to freeze during playback. Because not all of the 20 discs have been viewed, it's possible the percentage of discs with playback problems may be even higher. No two discs are freezing at the same spot, or even in the same movie (there are 3 short movies on the disc).
I got no errors during burning, but I did not 'verify' each disc after burning, either. I did play back my 'master' disc on my home DVD player to make sure it was OK before using it to create a disk image - which I used to burn all the other discs.
Some of the discs I burned from the disk image using Toast Titanium 6.1.1, until I discovered Apple's Disk Utility was actually a little faster. No way to tell now if the 'bad' discs are all from the same burn software. Though both Toast and DU gave me an option to burn faster than the rated speed, I used the rated burn speed of 8x, and I did not do anything else on the Mac while burning the discs.
My first thought was bad media. I used both Memorex and Sony DVD-R media (Taiwan) - there is no easy way to for me to find out if all the 'bad' disks are one brand or the other - but hopefully these brands do not have a 20% rate of defective discs.
My second thought was format-player incompatibilities (-R vs +R), but replacement discs, using the same media on my end, solved the problem for most people (one person's replacement disc froze, but at a different spot than the first one).
My final guess - I wonder if the playback problems might have something to do with the stick on labels I used? These are a Memorex brand product called "CD&DVD" labels, but the fine print on the back says: "Warning: Using a Standard or Full-Face label on DVDs may result in the disc becoming unreadable."
Any solutions?
Quicksilver G4, 867 Mhz   Mac OS X (10.4)   Pioneer DVR-108 (not OEM), firmware 1.20, PatchBurn profile

Answer 1

I just wanted to add my 2 cents. I haven't been on this forum for months. I've been happily making DVDs in batches of 10 -50 to distribute. I've been making them in my emac. Occassionally I'd get ones that wouldn't play in a client's player. The solution was to send a replacement. Usually that worked. Often I'd send a replacement that wouldn't play in one client's player but found that the disk would play in another client's player. The worst case was when the ist three DVDs I sent to one person wouldn't play, but the fourth did. But most of the time, the second one I'd send worked fine (All of these were made in the same batch from the same media (usually Fuji or Verbatim).
Recently I started getting lots more than usual complaints about problem DVDs. I checked out a bunch of them by actually playing them on both my computer, and a stand alone Cyberhome player. They were all made from a particular batch of Fuji media. Now I've previously burned hundreds of playable DVDs made from Fuji media, so I imagine it is just a fluke. (I hope) Some of them would play perfectly all the way to the last 5 minutes of an hour long presentation, and then start stuttering. Some begin stuttering in the middle. Several wouldn't even start up in my cyberhome player. Most of them would end up freezing at some point during the stuttering. The stuttering was never at the same exact place on any of the DVDs.
As an aside, I discovered something that I didn't know was possible. When a DVD froze in my cyberhome player at the menu stage, I'd push the eject button, remove the DVD, and the menu frame was still visible unchanged on the TV until I turned off the player or put another DVD in! I guess there must be some sort of cache in the player that stores the image. Very interesting. I've never seen that with a normally functioning DVD.
I also played each defective DVD in my computer to compare. One or two managed to play all of the way through on the computer, but most exhibited similar misbehavior on my emac. I'd say that, in general though, they all played a bit better on my computer.
Then it occured to me that there was another possible explanation. I was burning these from a disk image file that I had stored on an external HD. Whenever I needed a new batch of DVDs I would copy the disk image file back onto my emac from the external drive, and use disk utility to burn the disks. What if the disk image was corrupted? That might explain the problems.
Another thought that occured to me was the perhaps the process of burning a dozen or more DVDs in a row might cause a heat buildup in the burner and affect the burning in some way.
So I retrieved a good DVD made in an earlier batch of Fuji, made a new disk image of it, and left the image on the computer and didn't transfer it back to the external drive (on TDK media, because that's all I had sitting around), played the copy back on both my computer and Cyberhome player to make sure it worked perfectly. I then generated another dozen copies.
You may wonder how I had enough time to do all this. I'd just put a DVD in the player or my emac and listen to it while doing my ordinary office work. If I heard stuttering(it was my voice on the DVD) I'd instantly notice. I did this all day for a couple of days.
So anyway, I played 5 finished TDK disks all the way through today and they played perfectly. I guess the next test is to use the disk image of the same DVD from my external drive to see if i also get a good burn from it on the same TDK media and burner.
I did have time to do one other test though. I took a couple of DVDs that played well and put paper lables on them using the stomper system. They still played perfectly on both my computer and Cyberhome player. I'd speculate that paper lables are probably okay if they are applied perfectly, perfect centering, no air bubbles, good contact, and the disk stored in clean dry area. I've seen other peoples' CDs or DVDs with paper lables that had become wrinkled from exposure to high humidity and/or heat. I can imagine that they would tend to malfunction.
One client with a certain brand player actually took the "offending" DVD down to a AV store, and bought a replacement player that WOULD play it. I do think that it is interesting and useful to know that one brand player will play a particular particular DVD and another won't.
Since I make batches, I'm considering buying a couple more different brand DVD players, and then doing a bit of quality control - Trying out sample DVDs on all players before I mail out a batch to clients.
I hope that my observations might be useful for others.
emac 1ghz superdrive   Mac OS X (10.3.9)