Unhappy [HELP]Stock Settings apk Not Installing

Hello all. I recently used the modded settings apk made by Balliboxer for our Grand Duos. Later, when I tried to replace it with a stock settings.apk, the settings app dissapeared from my phone and even when I click the settings icon in the notification bar it doesn't open.
Now, I used root explorer and moved to system/app and found SecSettings.apk there. But when I changed permissions to rw-r--r-- and clicked install after mounting R/W, it says "APP NOT INSTALLED". Pls help.