write protection

I have an Ultra 32GB USB drive that has worked fine until about 2 days ago.  Now it is read-only on my Windows 8 machine and an XP machine.  Other USB drives work fine and do not show as read-only.  BitLocker shows it as read-only but as unprotected, and gives no provision to unlock it.  I have even loaded the MBAM program to no avail.  How can this be fixed???