Why is my iMac no longer recognizing Memorex CD-R and DVD-R media that it burned previously?

By the way, the Memorex CD-Rs are 40x rated, and the DVD-Rs are 16x rated, though they were all burned at differing speeds, I most often burned them at the highest rate possible, but I know sometimes when experiencing issues and making a few frisbies, I'd slow it down and burn slower. So I don't know what speed the discs I'm trying were burned at. Also, this might sound crazy, but in the past when this sort of thing has happened randomly with a CD or DVD it sounded like it was spinning it up way too fast and then spitting it out, so before I've tried to force the computer to give it a longer chance trying to read it by bogging down the computer - inserting the disc while performing a complex photoshop render, things like that, and it's actually WORKED. It isn't spinning these discs up to 500 mph and spitting them out, but I decided to try the bog down trick anyway, and I got it to read a DVD - it tried reading it for a good minute instead of 20 seconds and it loaded instead of just spitting it out. So I finally got one disc to load after trying about 12 different CDs and DVDs over and over and over again. I don't know if this means much since I basically just got lucky, but I guess it means it CAN read one if it really wants to, the question is how to make it want to on a regular basis, ha.

Thank you very much for your response, Klaus1. Yeah, when I was searching the forums for an answer to this problem before finally posting, I gathered that Memorex blank media isn't recommended and of poor quality, unfortunately, which is of course too late to help me with my current problem, but knowing that now I'll make sure I don't continue to use them in the future. I used them for many years, as long ago when DVD burners were first available I had a very hard time with Toast successfully finishing a DVD-R on an internal Panasonic 2x burner on my G3 tower, and for some reason I had good luck with them (Memorex). And then I had a lot of them on hand and they've stood up well over time (not flaking, etc.) so I kept using them over a few Mac upgrades. It also had to do with DVD players we had being compatible and able to read them.

Anyway, I'm rambling, point being I used them for lots of various reasons, but I should have kept informed in the more recent past and learned the fact that they're a poor choice and switched, my own fault. I just don't want to look totally stupid, like as if I had chosen them originally for no reason.

I went ahead and reset the NVRAM and also reset the SMC, and I had tried my cleaner disc with little brushes earlier today for the heck of it, too, but no luck still. The drive just changed it's mind and no longer likes the Memorex discs, apparently end of story and no changing it, sigh. It still really baffles me that it had no problem with them for nearly 6 years up until a few months ago, the last time I used one. So weird.

And no, I don't have the data on the discs stored anywhere else, so it's access them or nothing. I rummaged around and found an external 5.25" firewire case, and I do have a PC (yuck) I can borrow the internal dvd drive from and toss in the case and hook up to my iMac to see if it will read the discs and let me directly re-burn them to better media. I used to be very knowledgable about hardware and Macs in general, but I admit I haven't kept up my knowledge, and I don't know whether that will work - if my iMac is spitting out the discs because the drive doesn't like them and therefore a different drive might work, or if it's spitting them out because the system doesn't like them and switching drives will do nothing for me?

If not then I'll have to resort to finding another Mac I can hijack for a long time to re-burn all these discs I need, as obviously a machine with one drive is going to take a long time - putting in a disc, copying it to a local drive, ejecting it, putting in a new blank, and re-burning the data about 250 times. And a lot of baby sitting the machine as I don't have a robot to keep doing it for me. Sigh.

Thank you again for your advice, I greatly appreciate it even though I still struck out.

Thank you very much for your suggestions, Baltwo, I tried them and composed a response to you and Klaus1's similar advice as a reply to Klaus1's post, but I wanted to post a reply to your's as well so you'd be sure to get an email letting you know as well. Thanks again, really appreciate it.

For anyone browsing this thread trying to find a solution to a problem similar to this, I have an update on a final fix for this problem.

I found a firewire 5.25" external case and a Memorex 40x CD-R/+R/DVD+R, DL,recorder and hooked it up to my iMac, and it reads (almost obviously) all of my Memorex CDs and DVD's as well as a house brand DVD DL spindle I had, and all other brands of media I've previously recorded on including but not limited to Sony, Maxell, Verbatim, and a bunch of discs with green, blue, silver, gold, and a purplish reflective background. My internal Superdrive has always been picky and problematic, I had it replaced twice under warranty for failing to spin up and a third time off warranty myself for the same problem, refusing to spin up and read any discs or show any signs of life.

While Memorex blank media might not be very well regarded, I have to give high marks to this Memorex DVD burner drive. It's never given me a single issue reading or writing to discs and if you need to replace your Superdrive, you may want to consider going with an external like this Memorex instead of buying a laptop internal drive that fits in your iMac. I've had much better luck with this drive and it's a lot cheaper being full size.

So, my discs didn't all fail at the same time, my internal Superdrive just decided to stop reading them for apparently no good reason since they work fine on the Memorex drive. I can't knock Apple, I've been a die hard rabid fan since my first IIgs back in 1984, but in this one case the internal Superdrive that shipped with the early Intel-based Silver and Black iMac's (mine is 2007) is kind of crap. That's the end of my problem, solved!