I need to make a USB flash drive writable – not write protected

I have a USB flash drive (shows up in device properties as “Generic Flash Disk USB Device”) that is currently write protected. It was being used for ReadyBoost on Windows 7 64 bit.
Somehow it is now not able to be used for ReadyBoost and also is write protected.
There is NO read only switch on the device.
How can I make it writable again so I can use it once more for ReadyBoost on Windows 7 64 bit please?