Copy the VIDEO_TS folder from the DVD to your hard drive and see if they'll import from there. If they do then you are probably correct that it's a problem with your DVD Drive.
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What version of Premiere Elements are you using and on what computer operating system is it running?
Further details from you will define the issue.
I wonder if you have a problem or if you are just misinterpreting what you are seeing.
Pending the necessary details from you, I will use Premiere Elements 12 Windows 7 64 bit in the following example.
No matter what DVD you insert into the burner tray and then use Premiere Elements Add Media/"DVD Camera or Computer Drive"/
Video Importer, you will be greeted by the following dialog before the Video Importer is available for use
With your full knowledge that your DVD is not copy protected, you should be able to click OK, have the Video Importer
open and become populated with the thumbnails for your VOBs.
Are you seeing this dialog under the circumstances? Are you clicking OK? And what happens after
that as you wait for the Video Importer to open the files in its dialog (may take time)?
That message is not telling you that your DVD is copy protected. It is just telling you "just in case". In your case,
if you know for sure not copy protected, then you are OK.
What versions of Premiere Elements and on what computers are involved in your comparison of the "will" and the "will not"