[MacDV] DVD problems

[Robert & Susan Lloyd]

I've been burning DVD +R DL.  They play fine on my macs, both layers.  
They lose the second layer (apparently) when I try to play them on My 
Dell pc (it plays the first half fine).  I've tried two different makes 
of DVD: verbatim and (I think) memorex. I've tried burning them with  
DVDStudio Pro, with disk utility and with Toast.  No difference with 
this problem.  I'm quite sure that the DVD player on my Dell should 
play  them.

Any suggestions of what I might try next?  I'm trying to get a working 
copy to the person who is funding the replication, and it's nerve-wracking.

If the DVD is replicated, will that solve this problem?  How do I know 
ahead of time?

BobLL