Well, it might be a little different to the one I fixed; what I found was when adding FAT32 support to the Boot Wizard and I was testing it on my notebook with an SD card reader and an SD card inserted, the Boot Wizard would fail.
There were actually two problems: one was when enumerating the available drives, it asked for the manufacturer ID of the disk and since the SD card driver didn't supply one, the boot wizard failed and quit. The other problem was that after I resolved the first issue, I tried using the Boot Wizard to format the SD card and that failed due to a different operation the SD-card driver didn't support.
Now, if you got to actually select the USB device you wanted to format then it might not be exactly the same issue I saw, but it might be related. Something that's definitely worth checking is what drivers are being used by the particular storage device you have inserted (there will probably be two; a bus-type device that deals just with the USB host controller, and a mass-storage device driver to deal with the memory stick itself - the latter is the one that is probably most significant).