Sony DAV C450 "Dirty Disk Error"

[KailuaKid]

Living in Hawaii, I create Photo Shows for Family & Friends around the U. S. in various states. I use Memorex DVD-R 4x 4.7Gb. Everyone can play the shows on their DVD player except the one in Calif. They have a Sony DAV C450 DVD Player and they keep getting a message saying Cannot read disk - Disk is Dirty. Another member in Alaska has an older model Sony and everything plays fine. I heard Sony is supporting +R DVD formats. Can they be making their newer version to only play +R and not -R ? They can play the DVD on a Laptop but not on the Sony C450. Can anyone give me a good course of action for our Calif Family.
Thanks

[davideck]

How much data is on the DVD? I have a Sony DVD Changer that reports "Disc Dirty" Errors on DVD-Rs with capacities beyond 4.3GB. If I burn the same project on a DVD-RW, it plays fine.
I also have an earlier model Sony DVD player that plays these DVD-Rs.

???

[KailuaKid]

I used only about 2.4 Gig of the 4.7Gb of the DVD.