Macbook Pro won't read SOME commercial DVD's

Question

I found some people with similar issues, but no one with my exact problem, so I thought I would post it here.
I have a MacBook Pro that I got in November of 2007. Recently I noticed my drive stopped playing certain discs. I did some test and determined that it will play/write pretty much anything you throw at it except for some commercial DVD's. I actually brought it to the apple store and foolisly grabbed some dvd's at random, assuming that NONE would work. The one's I brought mounted just fine. Since I couldn't replicate the issue, I couldn't get much help. He said to try logging into a different user, I guess to determine if there was an issue with my Library. I tried that, it does the same thing regardless of the user.
Basically, some discs spin, and spin like the computer is struggling to read it, then it spits it out. Young Frankenstein and X-Men: The Last Stand, work fine. Children of Men doesn't (it used to work just fine).
I initially noticed the issue when trying to install the digital copies that came with my Back to the Future Trilogy boxed set. Back to the Future's digital copy disc mounts fine. The discs for Part II and Part III don't.
I doubt the drive is busted since so many discs work fine and it isn't ALL commercial discs that won't mount. Only some. My theory is that it's software related. Maybe something with reading certain encoding.
This is the second time I had this problem. The first time I read that verifying and repairing disc permissions would fix it, and it did....but now that doesn't do the trick.
It is consistent though. The same discs either work or don't work EVERY time. I thought maybe the lens needs cleaning. I read conflicting things about using lens cleaning discs in slot load drives so that's a last resort. But I imagine it wouldn't be so consistent if it was a dirty lens. Also, other players I've had with dirty lenses just skipped or had a disc read error of some sort. I don't get any errors.  I also ran the Hardware Test on my OSX Install disc, which found no errors/issues. I wonder if it would have detected my drive as an error if it indeed was a hardware issue? Makes sense to me, but I'm not sure what the Hardware Test tests exactly, if the drive is included in that.
Any suggestions? I saw a thread from 2006 where someone suggested that deleting (Library/Preferences/com.apple.finder.plist) helped him, but I am really hesitant to delete an item from my Library. That just seems like asking for trouble and I'm not sure what my finder preferences have to do with my DVD's not mounting.  Next I will probably try resetting my SMC. I'm not sure how that could help either, but it's a suggestions I've seen floating about and it's easy enough to do.
Here are some of my specs:
Macbook Pro, Intel Core2 Duo, 2.4 ghz
4gb Ram
Boot ROM Version:    MBP31.0070.B07
SMC Version (system):    1.16f11
MATSHITA DVD-R   UJ-857E:
  Firmware Revision:    ZA0E
  Interconnect:    ATAPI
  Burn Support:    Yes (Apple Shipping Drive)
  Cache:    2048 KB
  Reads DVD:    Yes
  CD-Write:    -R, -RW
  DVD-Write:    -R, -R DL, -RW, +R, +R DL, +RW
  Write Strategies:    CD-TAO, CD-SAO, DVD-DAO
  Media:    To show the available burn speeds, insert a disc and choose View > Refresh
Thanks. Sorry for the long and overly thurough post, but I thoguht that might help get me better help. Any input is greatly appreciated as it may save me the hour long trip back to the apple store.

Answer 1

I'm also having the same exact issues with some commercial DVDs and music CDs. It continues to read DVD-RWs but around two days ago it stopped reading commercially bought discs.
I've tested with brand new DVDs today (out of shrink wrap in pristine condition) all of which have the same region and have been tested on a DVD player, PS3, and another laptop without any glitches but only some of them played on my Macbook and the others would either spin for a bit and then ejected or it would read them as blank discs where the 'You inserted a blank DVD' message comes up.
I also tried testing older DVDs that used to play fine on my Macbook but only some of them mounted.
I then tried the following cleaning methods:
- Laser Lens Cleaner
- Compressed air
- Credit card with iPhone cleaning cloth
All of which failed to fix the problem so it's safe to assume this isn't a dust issue, the driver have also been very lightly used as I have only watched a handful of DVDs on it and written less than 10 DVD-RWs since I first purchased it in 2009.
My warranty has expired and replacing the drive would cost over $250 which I currently can't afford, therefore I plan to buy a cheaper external DVD burner but that is only a temporary workaround and I still hope for a solution other than replacing the driver.
Here's my info:
MacBook, Intel Core 2 Duo, 2 GHz
2 GB RAM
Boot ROM Version:    MB52.0088.B05
SMC Version (system):    1.38f5
MATSHITA DVD-R   UJ867A:
  Firmware Revision:    KK08
  Interconnect:    ATAPI
  Burn Support:    Yes (Apple Shipping Drive)
  Cache:    2048 KB
  Reads DVD:    Yes
  CD-Write:    -R, -RW
  DVD-Write:    -R, -R DL, -RW, +R, +R DL, +RW
  Write Strategies:    CD-TAO, CD-SAO, DVD-DAO
  Media:    Insert media and refresh to show available burn speeds