Is there a menu item which suggests you can do this ? I'm not sure why but some cameras will allow one to transfer images in one direction, not the other. Odd.
The way round it is to use a USB cable (or the Kodak dock) to transfer the image to your computer that way. Conceivably you could then copy it back to the card via the computer. But be careful as cameras save images in one jpeg format and the computer may save them in another so the camera almost certainly won't be able to read images that have been treated in any way on the computer.
You don't quite make it clear why you want to transfer images from internal to removable memory -- unless like me you've acquired a Kodak without the dock or cable and are using a card reader instead. This happened to me and I solved it by filling the Kodak's internal memory with test shots so that anything after that would inevitably go onto the memory card.