not reading certain dvd-r

i am trying to burn backups of my movies. I had 5 dvd-r memorex and 5 dvd-rw memorex. Both burned fine. I recently bought a pack of teon dvd-r. my dvd burner is a Khypermedia. Now the new dvd-r i just bought dont seem to read at all. After i burned the file to the HD, i put in the new black dvd-r, and in dvd decrypter, no info to the right came up, and i coudln't burn to it, cause it said no medium inthe drive. I tried about 10 of em all the same. I put in the memorex, it read. Now the new dvd-r are Teon / Khypermedia. I find it out my Khypermedia dvd burner cant read khypermedia mediums. Would anyone know the cause to this?