Optical drives slowly being destroyed/destroying themselves

Question

Well unfortunately I have only had my computer back for a day from getting repaired (again) and this 1 week and 2 days-old optical drive is doing the same thing the old one did before I had it replaced.
My old one was okay in the beginning, but then when playing DVDs it would start repeating a little scene of the DVD (different for every DVD really) and then it would start skipping over "damaged area". However, that area would NOT be damaged area, just something the drive couldn't read and decided not to deal with. Then, when it finally tried to skip over too much "damaged area" it would just reject the DVD completely and wouldn't try to ever load it again, even spiting it out if I tried to put it back in.
The old drive also could not read brand new copies of the same DVD. So whether I bought a brand new one, just opened the package and put it in, it would not accept it. It even did this to CD's also. So once I was able to, I had the optical drive replaced at an apple store.
Unfortunately as soon as I took it home from the store, the fan started to sound like an air conditioner. You could even feel the air it created inside on the outside of the computer. So, I took it in once again and waited a week for it to be repaired. Well, I just got it back yesterday. The things replaced were the temperature sensor, the cable for the sensor, and the LCD screen (for some reason).
Anyway, I try a few of the DVDs that the old drive wouldn't take anymore on this "new" drive. It messed up a little on the first once but I though "whatever". It was fine on the 2nd one. Then came the third DVD. As soon as the player started the infamous "repeat the scene" started once again.
... what? So I was hoping beyond all hope that it was the DVD. So I put it into another leopard imac 21 inch 2009 (only 3 inches smaller than mine) hoping that the DVD would do the same thing that it did on my computer. Nope. It was absolutely perfect on the other computer, no repeating scenes or anything.
Now, if you have stayed long enough to get to here I thank you because here are where the questions begin. I have already scheduled another appointment for my computer at the apple store. But I still have some questions.
Could it be repeating because I have a 24-inch imac?
Is there something that could causing the optical drive to slowly destroy itself? Like my hard drive perhaps? Is it perhaps programmed to do this?
Most important, if this keeps on repeating, should I shell out money for a new imac (since I doubt apple would just let me replace this one)? Or should I just keep the computer without a working optical drive?

Answer 1

Taking your questions in order:
1. It is happening but not because you have a 24 inch iMac.
2. Yes, something else is causing it but I sincerely doubt it is your hard drive.
3. No macs or the optical drives inside them are not programmed to do that.
You might have to shell out some money to replace the drive if it out of warranty.
Now my problem is this. I have a Power Mac G-5 2.0 GHz and quite recently the DVD player application for some reason stopped working. I kept getting this error: Initialization error: Valid drive not found (70012) after much searching and finding no answer, I decided to to buy an external DVD writer/player but the DVD application would still not work. I found out that I had version 5.0.1 and downloaded the Mac OsX 10.5.8 (which I am using)combo update and using Pacifist re-installed the DVD player. Before doing that I trashed the application and all revelent file like the plist file out of user/library/preferences. Now I get an error but it reads: ?? ??-10960. I have looked here but no answers. OH I have vlc so I can watch things but I want the DVD player application working. Does any one have an answer?