I don't get this (tech thing)
 

So, I decided to revisit a wedding video DVD I did in 2004. Neither of my two Macs would recognize the disc. The superdrives just spun a around a bit before spitting the disc out. Yet my worthless Phillips DVD player had no problem reading the disc.

For the heck of it, I made a copy of the 04 disc in my duplicator. Both computers had no problem reading the duplicated disc.

I have no idea who manufactured the original disc. The copy was on a SONY Disc.

Does anyone have any ideas how this could happen?

Home brewed DVD's are odd, fickle beasts. I learned a long time ago that you just never know when a self burned DVD will work and when it wont. I've had plenty of "good" media not work in certain players, and plenty of "cheap" media work in just about everything. You do tend to have better luck with the more expensive media, but there are so many different players on the market there's no telling when your disc will or wont work. That's just DVD's for you.

It got so bad at the company I formerly worked for that with critical projects (think corporate presentations) we used to burn 2 brands of +R's and 2 brands of -R's for the client. One of those discs was bound to play in something... you hoped.

The disc was burned on a mac? There was (at least) one iteration of OSX (10.3.1??) that gave this problem - discs played fine everywhere except on a newer version of OSX. Duplicate the disk on an external burner - problem gone.