DVD won't read...won't create avi thumbnails

I have a Emprex DVDRW 1116IM F/W: A091. I’m having problems backing up my videos. All my videos (Xvid/Divx) are about 700MB and I burn six of them on Sony 16X DVD+R disks. Most of the time I don’t have problems, but now I’m starting to notice more “errors”. When I say “errors”, I mean when I load the disk after its burnt, explorer starts freezing or the movies on the disk won’t create thumbnails.

btw, I use Nero 6.6 to burn and Nero never reports any burn errors.

Can anyone help?

Do you verify your discs after burning? What is the MID of your Sony discs?
That freezing may be Explorer/Windows problem. Do they work in another computer?
Try to install the newest firmware for your drive.