I'm having the same problem. I have a 2011 MacBook Pro that I just upgraded to mavericks. I'm using the same 16gb Kingston DTSE9 drives. I have two of them, one was already formatted to fat32 through disk utility, and would show up prior to mavericks. The other drive I just formatted to fat32 this morning through the boot camp utility. It showed before I loaded the boot camp installer on it, but when I put the drive back in, the computer would not recognize it even through disk utility or the diskutil list command in terminal.