"Skipping Damaged Area" error on DVD playback

My new 24" Intel iMac (early 2009 version) has an intermittent problem when playing any DVD via the DVD Player application. The message "skipping damaged area" appears for a second or two, then video momentarily freezes, then it continues from where it stopped. This occurs with all the commercial DVDs I play, and most of the DVDs are new (i.e., not damaged). I've reset parameter RAM, disconnected all peripherals but the factory keyboard & mouse, uninstalled Norton AV, deleted the DVD Player temp files in the administrator's library folder, and run the DVD Player from a newly created user account to rule out bad user pref files. The results are the same. It'll play fine for about 30 minutes, and then skip once or twice within a two minute period, and then run fine for another 15-30 minutes. This occurred with OS 10.5.6 and with 10.5.7 (latest system updates installed as of yesterday). I called Apple Support and they said to drop it off at an Apple store for a few days to have the optical drive diagnosed. I'd rather avoid being without the machine, so I'm trying to determine if (1) others have this same issue (meaning it's software related or "normal"), and (2) if there's anything else I can do on my own to fix it. Any help would be appreciated. Thanks!

Message was edited by: Doug in MD