Thank you for your quick help. I'm trying to delete the found.000 folder as I write this. It seems to have great difficulties with it (extremely slow), the same as when I try to access it through the device. The recycled folder is easily accessible through the Cybook and doesn't seem to cause any major fallouts, is also totally empty.
What if the Cybook can't delete the found.000 folder ?
(Hope it can, but just in case the thing decides to bite my butt)