I had an odd occurance last night. I had a little icon show up in my notification bar that looked like an SD Card. I pulled it down, and it said (something like) "SD Card is unreadable, please format" I knew that it couldn't possibly be empty, but I thought with all the weird things going on, maybe something screwed with it. So I booted into recovery, and went into "install from sdcard".
Sure enough (to my relief) all my stuff was still there. I've got directory structure to keep all my flashing files organized, and CM10.1 still had appropriate files, as did CM10.2, SlimBean, and Carbon.
So I didn't re-flash anything, just rebooted back to system, and then I was able to access my card from solid explorer. I don't know what might have caused that, but it's the first time I've seen it.
Just thought I'd share, in case somebody sees this, don't just take your device's word for it and format your card. There's probably nothing wrong with it that a reboot won't fix.