DVD-Rs won't finish burning?

I have an ancient Dual 1.42 GHz (mirror drive doors) PowerMac G4. Never have gotten a newer model partly because it still works fine, but mainly because I just can't afford it... 🙂 Oh, yeah, running MacOS 10.5.8.

Anyway, I have been using it for YEARS to burn DVD-Rs, with pretty much NO issues, other than wearing out a couple of DVD writers (I'm talking literally hundreds and hundreds and hundreds of discs). But I've been having a **** of a time burning discs recently -- and it just started happening suddenly. Discs get not quite halfway through, and just hang up and won't finish burning. I even put one in before I went to bed one night, and got up the next day to discover that it had still hung up at about the same spot and not finished after all that time. I haven't had even ONE DVD-R finish since. It just started happening out of the blue -- I had not upgraded any software, or done anything at all to my knowledge to the computer between the last successful burn and the first one of these happening. I was actually copying a 7-disc set, and got the first 4 discs done, and ripped disc 5, and then ran into this problem when I tried to burn it.

I tried every remedy I could think of, and googled the symptoms and tried most everything I found that was suggested to others asking for help with similar problems:

trying blank discs from a different batch/package (there were suggestions to use a better brand of media, but I pretty much NEVER have any problems with the brand of discs I use -- beyond one, MAYBE two bad discs per 50-pack. But I thought maybe I had hit a bad batch near the bottom of the package that I was almost through with using, so I opened another package and tried those discs, but still got no love. And besides, they were ALL hanging up at pretty much the same point)

using different burning software (I basically always use Roxio Popcorn for DVD-Rs -- but tried Toast, Burn, Burnz, and Dragon Burn, and got the same half-done discs with all of them...)

zapping the PRAM

repairing permissions

this really made no sense, but I even tried copying different discs, in case it was something screwy on the disc that I was trying to copy when this started happening, that was making my machine freak out for some reason. And store-bought DVDs, already-copied DVD-Rs, downloaded ISO files and VIDEO_TS folders -- ALL result in the same half-finished discs...

even buying a new writer/DVD drive

And it still does the EXACT SAME THING -- even with the new writer! So obviously, there was nothing really wrong with the writer....

There were only two things I could find that I have not tried. One is using a laser lens cleaner -- but there's no point in doing that on the brand new drive. It's behaving exactly the same as the old one, so it's obviously something else (and I basically just wasted $ on buying a new drive...). The other is someone suggested replacing the optical drive cable, as it could be going bad. Well, I actually sorta did try that -- I went and got one from the local computer store, but it wasn't long enough, so I threaded it a different way to the writer temporarily just to confirm if the cable even WAS the problem, and it wouldn't work at all (I started the machine and the monitor wouldn't even get a signal -- ?!?!?), so I took it back and returned it. I'm guessing that this cable is designed specifically for this Mac? I already found out a while ago that the power supply is... So anyways, I've looked online, and can't find a whole lot of replacement cables for this old model Mac -- and the USED ones start at $20, new ones are $30 and up. I don't particularly want to go to the trouble and expense of ordering one, because I'm not even sure that's even the problem. Mainly since it still reads and rips discs with no problems, and I'm still able to burn mp3s to CD-R (it just won't burn DVD-Rs). I would also be having issues with reading and ripping discs, and burning to CD-R if it actually was the cable, wouldn't I? But I don't know what else it could be...

Does this problem sound familiar to anyone? Have any suggestions of anything else that might be the problem that I have not tried already? Or does it sound like it COULD be the cable? I'm about at my wit's end with this. I've probably wasted at least a couple dozen or more "coasters" trying to figure it out...