Freecom toughdrive "Cannot configure hard drive"?

I have pword encryption on my 500GB Freecom Toughdrive, and it's never been a problem before now. Each time I've always gotten the pword right. I hadn't used it for a bit, and was going to put more stuff on it today. So I plug it in, guess my pword as usual, and it comes up "Cannot configure your hard drive. Please check your pword". I have ended up writing about 50 possible pwords, and it says this for each one. Given that I always get it right, I'm figuring that my pword isn't incorrect, something else is. What might be causing this? I KNOW my password's right, unless it's mysteriously been changed somehow.