[Q] Sd card 0 bytes available! topic

I have an Xperia C. I wanted to do a backup using CWM, but i got "error while making a backup image of /data". So i searched online for some help some fellow said "wipe dalvik-cache, do a "fix permissions" and then retry the backup.".
I tried that and then when i tried to do a backup it said error 0 bytes available or smoehting like that. I switched on the phone to check in the storage and same thing 0 bytes available. I even tried to connect it to pc but same thing, and when i try to open albums it says memory unmounted or unavilable.

device memory 0 bytes topic

Just rooted the phone..havent installed or changed any rom or software etc...
i unrooted the phone after getting this problem can anyone please help me get throught it

device details:
Samsung Galaxy Grand-I9082
version 4.2.2

i just dont know how to flash a rom..
just think that im new
so plss give me step bu step procedure

thanks in advance.