I hope they actually update Leopard so you can just drag and drop files into the iDisk rather than having to use an FTP program.
I've never been successful in uploading a file to my iDisk using Finder.
I've got to say that you might have a problem with your mac then Kilamite, because for me in Leopard, I simply drag and drop to iDisk, and it always appears in finder when I'm online.