Dvd burner not reading some DVDs

Okay I got an i/o magic dual dvd burner±r /±rw
windows xp svs pk2
it reads most commercial(store bought) dvds but it didn’t read Garfield today
Used NeroInfoTool and it says teh disc is blank. I put a Hentai flick in(made in Taiwan) and it wouldn’t get read neither(same message…blank dvd) tried clony xxl and it couldn’t tell me what protection it had
question is …y would some DVDs be read and some won’t(come up as a blank disc)
symptoms: dvd just spins and spins…a couple minutes later the blank disc message comes up
tried region decoders,anydvd…dvddecrypter…adjusting region…adjust dma…no results…dvd unit just won’t read disc…someone poin tme in the right direction…i already read teh 15 threads in this fourm with no answer.