I have the same issue as many of you. When I posted the problem to Sandisk technical support I received the following reply:
"… Thanks for emailing SanDisk Technical Support. It is our goal to make sure you have all the resources you need to get the most from your product.
I understand that you are getting write protection error while accessing your 16GB Cruzer Blade drive. This is because the flash drive has detected a potential fault and became write-protected to prevent data loss. There is no method to fix this, you will need to back-up your data and replace the flash drive; we do apologize for this inconvenience… "
Followed by procedure to return under guarantee. So now we know for sure that the problem can not be resolved.