There are a number of suggested fixes on the interwebs, though from the Sandisk Forum
“I understand that you are getting write protection error while accessing your Cruzer flash drive. The flash drive has detected a potential fault and has become write protected to prevent data loss. There is no method to fix this. You will need to backup your data and replace the flash drive.
Our team of developers is in combination with the OS developers looking into a solution to resolve this issue.
Please note that only a minor percentage of users are experiencing the write protection issue and these are the customers posting on the internet to find a solution.”
Looking further down that forum post, suggests that the Check Flash program by Mykhailo Cherkes, may fix the issue.
Update: no it didn’t work for me.