I'm guessing it's a Kprobe problem.
You'd be wrong then.
As has been posted many times, in many threads, Kprobe is doing nothing but displaying what the drive is reporting. If there's a problem with a specific disc, it's the drive's problem.
[b]One more time:
There are multiple factors that go into each scan:[/b]
1) The disc itself; what media type is it, how well was it burned, was the laser calibrated correctly, is the tracking within specs, what speed was it burned at , etc. etc. Is the disc perfectly flat, perfectly round, and is the dye perfectly even? If it's not, it may scan differently each time it gets mounted in a drive.
2) The scanning drive; does it "like" that particular media type, is it able to correctly track the disc and calibrate it's reading laser. What firmeware is used, is the drive hot or cool.
3) Scanning speed. When you combine all the above variables, scanning speed may be critical, especially if the disc is poorly written or difficult to track. Likewise, every scanning drive will have it's own preference for reading speed on a given media type.
The only scanning speed that conforms to the "official" specs is 1x, but comparing scans with 2 different reading speeds is useless in any case.
A "perfect" disc will always scan predictably, and scanning at different speeds will be just as predictable, (as will different burn speeds). But, there are no perfect discs.
All questions and discussions about Kprobe should be posted in the KProbe thread , or the interpreting scans thread, and preferably after the poster has actually read the threads.
This way, we don't have to keep answering the same questions over and over again. And, we all learn from the questions, and people who are looking for answers can find them.