When I loaded USB Loader GX yesterday I got that error message that's in the title of this post. I said great I gotta reformat this thing and reinstall my Wii/GC backups. So I did, I reformatted my WD My Book 500 gig. Partitioned it to work with my GC and Wii. Everything worked great. Turned it off went to bed.... Woke up turned it on then voila issue reared its head again. Now I'm guessing my 2 year old turned the thing on while I was asleep and my girl was watching him ( kid literally thinks everything is a touch screen ) and he hit the format button that pops up. Matter of fact im banking on this. But if he didn't do this... What could be the issue? Everything is pretty much up to date.