Chris:
If you go to the Lavasoft folder in programs, the previous file will still be there and marked as.
defs.ref.old
First remove the new/current file "defs.ref"
Then remove the .old extension from the other stored file, then re-start Ad-aware.
I have also checked the latest update, and contrary to my last warning it now appears that the new/latest file is still being marked as the old faulty file.
Personally, I would be inclined to wait until the next upgrade is labelled differently from "19.09.2006"