Ever since I've been on OS X (started at 10.0) I've successfully run System updates and not had any problems. I was once a Apple Certified Desktop Technician (right when 10.0 came out) but have since retired my tech support role and gone purely to the "skilled user" side. I ALWAYS repair permissions before and after an update, but I have never done a backup before any update because I have never had a problem - until now. I have 10.4.2 installed on my Powermac 450MHz G4 (AGP) with the DVD-RAM drive (slot-loading) and after installing the latest security update, my DVD-RAM drive will no longer read the 4X DVD-Rs I burn for backup (on my Superdrive at work). These discs have always read in my drive, even bootable backups of software I make so I don't scratch up my retail discs. Now the drive just takes in the disc and spits it out after a few seconds of spinning and hard drive crunching. It's fine with all my retail DVDs, both data and movies, but won't read a single burnt DVD. It is also reading all my burnt CDRs. I tested all my burnt DVDs on two other computers just to confirm there was nothing wrong with the discs and they are all fine. From the research I've done on support sites so far, it seems like the security update essentially "broke" my drives software component that allowed it to read burnt DVDs, but I'm not positive of this. I haven't found a single tech note or had anyone who could verify this is a problem for more than myself. It is likely that a lot of others could have this same problem, but haven't put a burnt DVD into their drive yet since the security update, or simply haven't run the security update yet because of all the other problems it's presented. I've already repaired disk permissions several times with no luck. I even booted up in OS 9 and it wouldn't read my burnt DVDs. That leads me to believe it's affected the firmware of the drive, but I don't know if that's possible. HELP! Thanks!