note : this issue only on iPad !
i try it on my iphone it work fine and move my files to other app
but on iPad i can't do that
You can use ifile and add permission to the folders in var/mobile/documents.
It has to do with the read, write, execute permissions in your file system. If you go into iFile and find the path listed in the torrent file (something like /var/mobile/Documents/caches/Torrents), then select the info button. You should be able to add "write" to the list of permissions. I also backed out of the file applying the same permissions to each folder in the path. I'm nor sure if that was necessary, but in the end it worked. I also selected "apply hierarchically" just to make sure it took. Kill iTransmission and respring and everything downloaded perfectly.