I can't make copies of my (I made them myself so they are not copy protected) data discs. Every time I try, I get an error saying "unsupported media type." Is this an actual K3b problem or a DVD+RW problem or is it just my particular Blu-ray drive? (it will let me copy commercial (i.e., movies) discs. Any help is appreciated.
I am wondering if the discs are actually closed properly? Or do data discs not need closing?
Dolphin shows all the files on the disc. Or does it have something to do with the actual discs themselves?

Thank you.

Running Mageia 5 64 bit with all the latest updates, including multimedia updates.

You can try another burn program?