Some of their USB drives have complementary software to turn on and off. If you've never installed or used such software, then it's 1 of 2 things.
1.) the drive has a CD-ROM partition that cannot be removed. This is needed for added functionality (encryption/security etc).
2.) this is a simple USB drive and it's been working fine until one day you noticed it was write protected. If this latter is the case, then the drive is about to break. Copy all data off of it, and replace (buy new or RMA).