Computer not reading some DVD's...

Alright, so I was going to rip the files off our old wedding DVD's today and work some magic on them as a surprise for our 11th anniversary. However, my computer is showing the DVD's as blank. My PS3 reads them fine and plays them, and my computer plays normal movies on DVD just fine so I'm kind of at a loss.

I'm going to try them on a different computer tomorrow and see if I can get them read when I'm at work, but if not should I buy one of those DVD cleaner packs? Will that even help? If anyone has any ideas I'm game.
I'd start by running a lens cleaner on the DVD drive. If everything is reading it fine, but your computer is not, it would point to an issue with your drive. Is it old, new, awesome, terrible?
What brand of DVD player and which OS are you running? Are the DVDs 11 years old, or just the pictures on them? Were they commercially made DVDs (like by a photo developer) or did you burn them yourself, and if you burned them yourself, what software did you use?
Running OSX Lion, it is an older SuperDrive, but it still plays the few DVDs and CDs I've put in it until I tried these. They are old video dvdrs. Nothing fancy, just home movies from years back probably made in iMovie. Like I said, they play fine in my PS3, just run right away, but they come up as blank on the Mac.

I'm going to try them in the external drive I have at work, and see if I can get my laptop to recognize them but I could also stop and pick up a lens cleaner kit at Target if people think those are actually useful.
It's also possible that the discs were never "finalized" properly, and so since there is empty room left on the discs, it is assuming you are looking to burn more data onto them. If it shows you there is less space available than an entire DVD, then that's probably what's up.

Hmm. I know they've played fine on this computer in the past, maybe something in the more recent versions of OSX are causing it? Maybe if I install a partition of leopard or something? Heck I could throw a windows partition on there and see if that works too.
Crap, I know almost nothing about Apple software. I've had problems similar to this on Windows machines, but it almost always came down to being physical media that was just low-quality enough that it had degraded to a point where a DVDR or DVDRW drive couldn't read them, but other players could.
Yeah, no, just basic DVD-R. I'm thinking that it's probably a combination of a old DVD and a old Superdrive that just couldn't quite handle it. Either way, it's all good now I guess.

I may still buy a lens cleaner though, just to give it a once over. Reviews are super sketchy about them though.