My DVD Player in my vehicle won't play DVDs I've created?

I have the entertainment package in one of my vehicles and not long ago it stopped playing my DVD's that I had created. I've tried burning to DVD+R & -R with no luck. I've tried burning at slower speeds with no luck either. I've tried cleaning the darn thing and nothing changes.

It used to work and it still plays all original DVD movies that I have, but anything else it won't. Any ideas?

Thanx