First time problem? I hate to be another statistic of a faulty 680, since I really like it, but it a very annoying issue that I don't know how to deal with.
Re-installed the latest firmware. That's about all I can think of to try. Also the hold switch doesn't seem to engage. When I switch it 'on' nothing seems to happen. I've never used it while recording, but seem to remember a message showing up, or at least an indicator, that it was engaged. I could be mistaken in that memory though. I'm wondering if this is part of the reason it won't turn off now.