Pendrive became write protected

Hello,

my pendrive became write protected...antivirus cant detect any virus.all the files and folders are now renamed with special letters(chinese,greek).Cant format the drive as it is write protected.I used diskpart but when I typed ATTRIBUTES DISK it is showing read only state as NO.so when typed ATTRIBUTES DISK CLEAR READONLY it successfully cleared but the problem remained same.
I tried using regedit....but I didnt find StorageDevicePolicies..so cant solve it...tried to format the drive using disk management but after formatting certain percentage it says some files cant be formatted ,so the problem rmain same.................please help me