DVDs I’ve burnt either read as “blank” when reinserted, or can’t complete the initial formatting.
I used to be able to burn & read both DVD formats. In fact, I have a few DVDs I burnt previously that Windows can read just fine.

With DVD +R:
Windows will go through all the steps of formatting the DVD, burning files to it, and closing the DVD with no problems… But when I reinsert the DVD, it comes up as blank, with absolutely nothing on it.

With DVD +RW:
Windows will start the DVD formatting process, then say it’s “unable to complete” it.

My DVD burner is listed as PLDS DVD+-RW DH-16A6S ATA Device according to Windows Device Manager, so it should be capable of burning/reading either DVD+ or DVD-, R or RW..

I checked for driver updates, but mine is current:
DEVICE MANAGER > (right-click device) > CHECK FOR UPDATES.

I have a Dell Inspiron 530 with Vista Home premium, & I was using Sony DVD +R DVDs & Memorex +RWs.

In searching online for solutions, I found a few posts from people complaining of the same problem… who say the problem began after a recent Vista update. Is this true? If so, what’s the fix?

What’s the fix, even if a Vista update didn’t cause the problem?

I would try the following
Uninstall and reinstall the driver
Try known good DVDs
Microsoft Fix it Solution Center: troubleshooting software issues
Use system restore from 3 days before the problem
You may want to try this, at least for a test
DVD Flick
Try from another user account.

Test your hard drive
Test Hard Drive www.carrona.org/hddiag.html or this test http://www.tacktech.com/display.cfm?ttid=287

http://support.microsoft.com/fixit/

For the DVD+RW I would try formatting one with Imgburn. Try burning with it and see if it works. I have Memorex 8x DVD+RW I use on 2 PCs. I initialize by doing a slow format with Imgburn. Then before burning anything to the disc, I do a Quick Erase using Imgburn on the same system I'm going to burn data. This eliminates any inconsistencies between the 2 machines. At least it's been working for me for hundreds of burns.