I recently had a problem with a "corrupt" FAT filesystem SD card - I reinserted it several times into the N800 but each time the N800 would refuse to mount the card as it was "corrupt". I mounted the card once (and only once) in a Windows XP PC where I could read all the files just fine, so I returned the card to the N800 where it mounted immediately and without complaint from the N800. I've no idea what changed, but seemingly the Windows PC silently "repaired" whatever the N800 was objecting to.
