I had the same thing just happen tonight...
I had the trial of DVDFab Gold on my PC and when it expired I went ahead and bought the Platinum (last Sunday)- It worked fine on the one disc I tried then. Tonight I had the same prob/message you did-but it did write/save the files to the DVDfab folder on my hard drive under the movie title. I also rebooted a couple of times with no luck; it didn't recognize any of the three DVD burners on the line... Then I tried to burn a disc of the saved folder using Nero 6 OEM and it worked! I did two more movies this way, checking them afterwards and they were fine, and DVDFab did NOT erase the old files/folders, it added new ones so that all three movies were still on the drive.
Tho in a way that was cool, it wasn't what I signed up for, so in the time it took me to wait for the registration email to sign up here on this board after seeing your post, for kicks I looked to see what version I had, ass-u-ming it was the latest (I mean it WAS last Sunday). It seems I had 126.96.36.199, not the latest .9. I did a download/upgrade of the new version, restarted the comp and all seems to be back to normal.
Hopefully this isn't going to be the norm with this program, since other than this hiccup I love it. Hope this helps... M