Found a solution for this problem..and i think is some incompatibility between MIUI 2.7.20 and the latest Siyah kernel as long as with different roms this issue wasn't there.So...i took out the SD card and i did a FULL format with computer , FAT32, of course and until now everything is normal. I am writing this just in case someone need this type of "fix", until the bug will be eliminated
Aah, okay. Glad it's working.