DVD Double Layer Playing problem

[brett stevens <brett@math.carleton.ca>]

I recently obtained a two DVD+-RW DL burners and decided to test them by
trying to burn a copy of Monster's Inc (which is a DVD we own that is a
DL disk)  They are the Plextor DVDR PX-750A  and the DVD-RW drive that
comes with the SONY VIAO VGN-SZ160P.

I used 

dd if=/dev/dvd of=DVD.iso bs=2048

to make the ISO, and

growisofs -dvd-compat -Z /dev/dvd=DVD.iso

to burn it.  

There were no reported errors at all during the burning process.

I can mount the burned disks on the either of the Dl DVD+-RW drives that
did burning, but my oldest DVD drive (which is only a DVD-RW single
layer burner) thinks there is no media there (it can play commerical DL
DVDs just fine).  I can play the ISO image with xine no problem and I
have used "diff" to verify that 

1) The ISO and the burned DVDs movie are the same

But I cannot play the burned DVDs as video anywhere, including the
drives that burned it one (with either windows or linux)  On windows or
a commercial stand-alone DVD player I get a frozen scene from one of the
previews with a stuttering text that loops after a few minutes.  With
either xine or totem it reports that this DVD is encrypted and
recommends that I install libdvdcss.  I have libdvdccs installed and it
is what I use to watch most commercial DVDs that I watch.  

Additional info.

dvd+rw-mediainfo reports

"Media Book Type:       01h, DVD-ROM book [revision 1]"

for both the burned DVD and original, so I don't think using 

"dvd+rw-booktype -dvd-rom -media /dev/scdN"

from Andy Polyakov's DVD+RW tools webpage will work (I have not tried it
though)

It seems clear that in terms of data and filesystems, I am burning
DVD-9s (DL DVDs) just fine, but not from a video playing point of veiw.
Does anyone know what is going on and how I can fix it?

regards
brett stevens