Good news! In MozillaZine Build forum http://forums.mozillazine.org/viewtopic ... 26#1604526
polidobj found the cause and a working fix:
1. Find ablock.jar whether it be in the xpi or in the directory where the extension is installed. I did the latter.
2. Edit settings.xml.
3. Find this line of code (there is only one instance in the file):
4. Add this line of code after it:
5. Save settings.xml back into the jar file and make sure it's still in the content directory.
6. Restart Firefox so it rereads the jar.