OK, i wasn't familiar with how WOPC worked, but i found a page on it; i get it now.
So, here are some more burning results. It seems to be mostly working better now, but there are still some quirks i can't figure out.
Here's my log:
<b>Burning a 4.3GB disc image to a DVD-R using DVDdecrypter:</b>
Speed is very erratic, sometimes climbing to 4x or 5x, sometimes dropping below 1x, but generally hovering near 2x. This image is on the Windows drive, which is on the same bus as the burner (unfortunately, it has to be, as my Windows drive is the only one currently formatted as NTFS). Thusly, it will stay at 4-5x more if i refrain from using other programs while burning. Also experiencing system slowdown again. Perhaps it's time i reformat one of the partitions on my other drives to NTFS for larger images like this one.
73% complete: speed has climbed to and is staying within the 9.5-10.6x range. Seems to work best if DVDdecrypter stays in focus.
Forgot to record overall burn time; somewhere around 20-25 minutes.
<b>Burning compressed DVD-Video to Fuji DVD+R using Nero:</b>
Emptying the partition these are on before formatting to NTFS to try large image files.
3.2 GB, attempted 12x. Time = 5:23
3.6 GB, attempted 16x. Time = 12:11
Took 7 minutes to get from 5% to 9%, then resumed proper speed.
(I've had this problem as well as a number of coasters when burning at 16x; that started happening long before my current problems.)
3 GB, attempted 12x. Time = 5:01
<b>Burning a 3.7GB disc image to a DVD-R using Nero:</b>
This one is on a drive on a different bus, and is quite fragmented.
Attempted 12x. Time = 5:58
<b>Burning a 4.2GB disc image to a DVD-R using DVDdecrypter:</b>
This time the image has been placed on the new NTFS partition, which is on a different bus from the burner.
Attempted 12x. Time = 6:29
Speed varies again, but this time in the 6-8x range. Average speed slowly climbs and reaches the 10-12x range at around 40% completion.
I am also noticing that my drive is occasionally refusing to recognize the -R discs. It seems i can usually get it to work by swapping it for a blank +R and allowing it to recognize the disc, then swapping back, but not always. I have no such trouble with +R discs.
(end of log)
It seems that my speeds are tolerable if the file is on a different bus from the burner, the file is preferably not fragmented, and the planets are correctly aligned.
I guess my problem is basically solved. I'm still not sure exactly what it was, but likely it was a combination of the transfer mode and fragmentation of the Windows drive and/or source files.
As a mentioned, a few things i still don't quite understand...
1) I know it isn't recommended, but i never had problems burning from a hard drive on the same bus before. Why now?
2) What could be causing the trouble burning at 16x? I normally burn at 12x, but it would be nice to know if this is something that can be fixed.
3) What might be preventing the initialization of blank -R discs?
The third point is the biggest problem. I've got a whole bunch of brand new, quality DVD-R discs, and half of the time it takes an act of congress to get the drive to recognize them (and i think we all know how speedy the legislative system can be). Anyone else have experience with such a problem?
Thanks to all who've made suggestions thus far; this forum in general has been a really big help!