First if you can't read it anywhere else, how do you know the disk is not corrupted or scratched or the dye has failed? You can't KNOW it's not an issue with the disk unless you can read it at a second device. Since you can't read it on anything (I'm assuming you tried 3-4-5 different DVD drives/computers or else you need to try more), I'm guessing the disk is bad, or the format the DVD recorder wrote to is unreadable by a computer. Did you try a component DVD layer or just one in a computer?
Did you check for scratches, smudges, etc...?