think this write protection error is due to some virus.
Steps to remove write protection for Transcend users
1) Go to download center of the transcend,here is the link
Type the model no. or part of model number you are looking for.
example: JFV30(all alphabets in Caps )
2) Choose other details like product type etc. and search for your product
3)Then select the product which which is most similar to yours from search results
4)Then download the mFormat utility. You will asked for serial no. if you dont have..enter this no. 1456784523
5) Connect your pen drive
6) run the mformat utility and select full format after full format your write protection will be removed. try twice or thrice if you can't correct at first time.
It worked for me and my friends....
Other pen drive users may visit there vendors site and download any fromat utility present there for your model.