burning problems.

Hi everyone, I've been using DivX player to burn DVDs for some time and usually find it works very well. However I've recently run into some trouble.
The CD drive in my HP Compaq6720S reads the disk and finds it to be blank. When I click to burn, it says "initialising" for a few seconds and then the disk pops out with the "congratulations, you have successfully burned....." message. Except, I haven't!
It's all over much too quickly and there is nothing on the disk. Insert the disk again and there are still 4489mb of free space.
Try another disk and the same thing happens.
Reinstalling divX software doesn't help.
I asked my local computer shop to change the CD drive but they couldn't find a compatible replacement.

I'm using Verbatim disks,
OS is Windows Vista.

I've seen other posts from users with exactly the same problem but they didn't get any replies. I'm hoping somebody out there can shed some light on this for me.

Thanks very much.