[Q] [HELP] Lost sdcard permissions - CWM

(Tablet model: Eken A90)

After restoring a backup image taken from an identical tablet (4.0.4) with CWM Recovery, the permissions on /mnt/sdcard are lost after each boot:

ls -l /mnt/sdcard
d——— system system 2013-01-24 23:08 sdcard

I can fix the permissions manually: [chmod 777 /mnt/sdcard] everything goes back to normal until the next boot.

I have tried "fix permissions" within CWM Recovery with no luck.

Any idea how to fix /mnt/sdcard permissions permanently?