Um, with all due respect, screw the verify function (for the moment)
Again, how do the discs perform in a Transfer Rate Test, a quality scan, and scandisc tests? If those tests go ok, and the verify function is valid, that would leave some issue with the data itself and not the actual burns, which could be a Hard Drive, maybe an IDE cable or driver issue? First thing's first though, run a transfer rate test. If the drive can complete the test then the data is readable, regardless of whether or not it actually matches the data on your hard drive.