Well here's some known fixes. Might help:
Help, My files i copied to the external drive are not visible on my pc?
The files are marked as system files, which windows default hides. Go to Tools > Folder options and disable the following option: Hide protected operating system files
Help, It won't copy
On the screen you'll see 2 directory listings. The yellow one is your 'active' one. You can browse through them with the D-PAD and enter directories with the X. When you press the copy button, the selected file or directory will be copied to the other current folder of the other directory listing. So make sure the other directory listing is always in the correct folder (index of /dev_usb000 for your external drive).
Also an important note: Be careful! It is a very dangerous tool if you don't know what you're doing. We are not responsible in any way!
Those are just fixes from the dev himself.