Problem with Platinum DVD's

[ikara]

Until recently the DVD-ROM drive an LG 8160-B was recognising any DVD's I could find to put in it.I am running WIN98SE and had some unrelated problem which I resolved.Since then the 2 DVDs made by Platinum disc corp. are no longer recognised.Any attempt to play them causes an error "No Disc in Drive"All other DVDs I have work fine. I haven’t a clue why this is happening.Does anyone hear know something about the differences found with DVDs that may be the problem.I have since also installed a DVD burner and it will play these discs fine.The drivers used by win98se is the same for both. I am not aware of a separate driver for the 8160. The internal software on the drive is v1.01, I can't find anything newer to flash the ROM with.It really escapes me what changed on my system to cause this?If anyone can shed any light on this for me I would appreciate it. Thankyou.