If, on the other hand, you have a flash device that does not have a write-protect tab (many do not) and it is showing as write protected, something bad happened to it.
That tab may be missing because it was built without one. There are a heck of a lot of threads out here about spuriously write-protected flash. If this is your case, some members recommend reformatting it. I personally recommend copying all the files off it and then putting it through a shredder; I wouldn't trust it.
Edit: Sminlal, you are so much more optimistic today than I am.