How to repair an Internal SD Card Partition to Perform Successfull Factory Reset?

[AC Question]

I have Samsung Galaxy y s5360.
I have installed CWM and Custom Rom of Cynagenmod on it.

When i go to wipedata/factory reset my Phone I face the Following Error

Formatting /sd-ext...
E:format_volume: make_extf4fs failed on /dev/block/mmcblk0p2

A samilar error occurs when i try to restore my Orignal OS from recovery manager.
E:format_volume: make_extf4fs failed on /dev/block/stl19

What should I do?