don't junk the machine, junk your crappy media.
memorex is absolute junk.
verbatim are the best DL discs at the moment. none of the other brands really match it in quality.
also, remember with DL burning, you have to make sure your program is correctly handling the laye rbreak. i wouldn't use nero for dl burning.
use dvd decrypter to rip in ISO read mode then load the .mds file back into dvd decrypter (or into ImgBurn if you have it) and burn in "ISO WRITE" mode.
this .mds file has the layer break information to send to the disc that way the layer break will be in the same position as the original.
sometimes if you put in your own layer break or if you let the program pick then you're running the risk of placing it somewhere that will cause erros on the disc.