Are the DVDs that you're trying good ones? I've seen a lot of discs that are really poor, and only some that are good (this is with blank discs for your own burning purposes). There are some tools (lsdvd, if I recall correctly), which can give a report on the disc that it reads. Might be worth trying it.
These are rented movies dvd's... All worked fine at the store when I took them back, and I rented some more, same thing, some will work, and the others don't lsdvd is not much use if fedora does not recognize that there is a disk in the drive. I would have thought if the drive it's self was failing then the reading of discs would be intermitent, but as it stands the drive will either always read the disc or always fail to see the disc. I thought it mightr have been a region code problem, but all the discs I have been using are from the same region. It seems to simply ignore some and accept others. -- Rob