It's late and I'm tired, and I can't seem to figure out how I did it... but somehow I lost ALL of my books on my pocket pro.

I'm sure it's something simple (or stupid

)...
So here's what I did. I had about 30-40 books on the SD card of my PP. I decided I wanted to rework my folders, so I connected the reader to my computer with the USB. I went into Windows Explorer, and deleted everything on the card. (I'm thinking that was not good, maybe I deleted something I shouldn't have?) Then I went into Calibre and got the folders set up the way I want them. I could see all 240 books in Windows Explorer, in their various folders. Then I disconnected (including clicking the little icon in the lower right hand corner of my computer that says to disconnect). I then looked at my Pocket Pro... and the only folder listed is Recently Read, and it's empty. I hooked it up to my computer again, and there are all the books and folders... so I disconnected, and I still can't see anything on the pocket pro. I thought maybe there's something wrong with my folders, so in Windows Explorer I copied about 4 of them over to the internal memory. When I disconnected I could see those on the internal memory, but the memory card still appears to be blank according to the Pocket Pro...
So what could I have done? I'd appreciate any help.

It's way past my bedtime, so I'm just going to put it away for tonight, and hopefully tomorrow when I look at it I'll see something dumb I missed tonight. But in case I still can't figure it out in the morning, does anyone have any suggestions for me? Thanks!

Oh, and I also tried putting the card directly into my computer (after powering down the PP), and I can see all the folders and books that way, too. Oh, and something else strange... when I hooked the Pocket Pro up to my computer and Calibre started doing its thing where it looks for books on the device, it would go up to 67%, then jump down to 20something %, then jump back up, and back down again... like it wasn't sure if there were any books on it, or not. I think Calibre is just as confused as me!

And as a last resort I just tried reinstalling the firmware upgrade, but that didn't seem to help either...