It could be that your JVC is picky...or bitsetting it may well help.
Memorex isn't the best media, though - for DL, I'd recommend Verbatim.
You can set the Booktype in Nero or ImgBurn, though you'll have to reset it to DVD-ROM for each DL disc you burn. At least, I believe that's how it is for the 4167B.
BTW, setting the booktype can only be done prior to burning...you can't change the booktype on an already-burned disc.