I have seen numerous posts on this form with respect to Dual Layer burning. I bought a bunch of Memorex DL DVD's and had no luck with Popcorn. I repeatedly hit Sense errors (Medium and Hardware) during the burn process.
There are a ton of posts that imply either you have a bad burner or the Media is lousy. In general, Memorex doesn't have a great rap.
I dug into this since I am a week away from my warranty expiration and wanted to ensure it wasn't a true hardware issue. I tried using Popcorn 2 to write a disk image and then burn the image however I had errors when using Popcorn to burn the image as well. It was very frustrating as I went through 10 blanks with various experiments.
My final solution that works is:
1. Use Popcorn to write out the disk image file.
2. Use DISK Utility (as Apple program that comes with OSX) to burn the Image file created in step 1.
3. I have done this 11 times now with no errors and the DVD's play in my home players (tested 2 players - JVC and Sony)
Thus, there is a problem with Popcorn. I exchanged emails with Roxio support however they seem unable to offer any real help other than try a different media or your drive is not working. Given I have 11 successful runs, I can't imagine either is the issue and that Popcorn is the cause.
Good Luck and let me know if this works for anyone else.