Make sure that you are using
Ad-aware SE Build 106r1 Note: If your version is 6.0 and not the SE, you need to uninstall and get the latest version from the above link.
[if not Uninstall your old Ad-aware first then install SE] Then use the
WebUpDateto get the latest Definition file
If you are using the correct version, then see this thread for more info and instructions.
http://www.lavasoftsupport.com/index.php?showtopic=1336