Did the sudo fsck.vfat -y /dev/sdb1 thing but it didn't fix the problem. At least it told me where the corruption was. I was able to mount the PW on a Windows box and do a Disk Check there. The corrupt files were in .Trash-1000, so I deleted that whole thing and now Calibre connects to it. YAY!
I was so afraid I'd have to reset the PW and reload all my books.
the check is in the mail!!