Here’s the message I get. I use a Kindle Fire with Jelly Bean 4.1.1 CM10.
please give me the permissions of your /system/etc/custom_backup_list.txt
command in shell:
ls -l /system/etc/custom_backup_list.txt
app/com.avast.android.antitheft.apk
I’d looked at this before and found it really weird.
please, i do not want the contents of the file
execute the command exactly as i posted above.
u0_a36@android:/ $ export PATH=/data/local/bin:$PATH
u0_a36@android:/ $ ls -l /system/etc/custom_backup_list.txt
-rw------- root root 36 2012-09-06 22:48 custom_backup_list.txt
Are you still available?
i also have a weekend, guy 
seems the permissions on custom_backup_list.txt are too restrictive. We will fix that in next program update. For now, either perform following command with system partition rw mounted:
chmod 644 custom_backup_list.txt
or just delete the file and recreate it from Anti-Theft.
I forget the Internet also has weekends 
Shell command didn’t work; “Unable to find file or command.”
Deleted the file, then did the re-write, backed up “successfully” the first time, fails at later attempts.
I do believe that the “successful” backup actually has no effect. I remember seeing these messages before wiping my system through TWRP 2.2.2.1 Recovery, but would later find out that the settings actually failed.
the issue with re-try failures will be fixed in next public update (we then set permissions correctly).
Thanks!