Unable to copy data into samsung ace mobile
I am trying to copy some folders to Samsung Galaxy Ace S5830. When I connect the mobile to PC and click button for "Turn on USB storage" at the bottom, it connects to computer and there is new drive showing in my computer. When I open it, it opens and I can copy files from it. But when I try to copy something into mobile it shows error "You don't have permission to perform this action". even on deleting something same error window pop up. but I can delete something in mobile when I select delete in mobile(i.e. when not connected to computer). I have tried switch off/on, remove and insert micro sd memory card, even tried on another PC. But error is same. I was able to copy data to mobile some days before. and I am able to copy data into memory card when inserted in other mobile, so it is not the issue of memory card.
So my question is "is there is a setting somewhere in mobile for write protection that I might have accidently turned on ??"
Other details : OS of computer : Windows 7 professional SP1 Mobile OS: Android OS, v2.3 (Gingerbread) Memory card: sandisk 8gb memory card (micro sd) class 4 Other mobile details are on http://www.gsmarena.com/samsung_galaxy_ace_s5830-3724.php
Please Help. Don't suggest restore factory setting as I don't want to do that.