GSII: Internal storage became read-only

Hello,

I have Samsung Galaxi S II GT-I9100
Android version 4.1.2
I got root access, CWM and SSH server installed.

Recently I tried to download an audio file over 3G. The download couldn't be completed and after then I wouldn't be able to download any file. I discovered I could also not delete any file from my internal storage which is sdcard0.
When I tried to change permissions on sdcard0 using SSH I typed:

Code:

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chmod -R 777 sdcard0

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and got this:

Code:

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chmod: sdcard0: Read-only file system

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Please help :) would be much appreciated.
Thanks in advance!