Why can't I burn DVDs on my 708UF any more?

I’ve had my 708UF since they first came out. I’m using Nero OS is XP, SP2. PC has dual processors (2.00 GHz, IIRC), 1.5 GB RAM.

I almost never have a problem burning CDs – only with DVDs. I was able to burn good DVDs most of the time until a couple of months ago (I went through almost a whole spindle of 50 Maxell MIJs with good results and then suddenly started having problems). Now I can’t burn a good one no matter what I try.

I’ve tried several different types of media. TDK, Maxell (MIJ), Taiyo, and a brand-new spindle of Sony (MIJ) just bought this morning, which resulted in uncorrectable error 31105.

I shut down all programs (except ZoneAlarm) when burning DVDs. I’ve tried burning files from my IDE drive and various SCSI drives (all internal). I tried hooking up the Plextor to my laptop and burning a DVD (I only have Roxio installed on the laptop, and I got the dreaded No Additional Sense information error).

I’ve tried both -R and +R media. I always burn no faster than 4x. (I’ve tried 8x, and the results are no better.) I’ve tried hooking up the Plextor via USB2 and Firewire. No difference.

Some of the files are .avi, some are data files (QuarkXpress, Photoshop, digital photos, etc.), some are drive images. I’m not copying commercial disks, so copy protection should not even be an issue.

I don’t know what else to try. I don’t have another DVD burner to experiment with.

When I burn DVDs, I often get no errors, but I do get a pretty awful-looking transfer rate test results. I’m attaching one or two (not sure I know how to attach more than one!) below.

Am I making too much of the transfer rate test results?? Is it possible that the DVDs are really okay, even though the TRT graph is so jagged? Checking the DVDs by opening or playing all the files is not a logical option – it could take several hours to check each disk.

Before I started having problems a couple of months ago, the TRTs were much smoother – the yellow line almost straight across, the green line a fairly smooth diagonal.

The only wild card I know about is the DMA settings. When I check my IDE controller settings, they are all DMA except for device 0 on the secondary IDE channel, which is set at PIO.

But I have no idea what device 0 on the secondary IDE channel is! How do I determine which devices are on which channels?? My IDE devices are my CD reader (internal), the Plextor (external), one internal IDE hard drive, and one external IDE hard drive. But I don’t which is device 0 or device 1 on either the primary or secondary IDE channels (I am NOT a technical person, to say the least).

If I change device 0 on the secondary IDE channel to DMA, and it turns out it’s not the correct device, will it screw up anything or will I just be able to change it back to PIO? I have no idea if the hard drives need to be PIO or DMA.

I would appreciate any suggestions. My next step, if I can’t solve this problem, will be to buy a new DVD burner, but I’d like to rule out other possible causes first. I really don’t think it could be media, since I have tried so many different types.