I'm also getting "Unable to install..." on my N800. I'm trying to install to internal SD, using MMC2 files. To be clear, is MMC2 the internal card on an N800? I've searched for more information on this without results. I'm using a 2GB SD, formatted on the N800, and although it says it's unable to install, I do see a .img file on the card. The external slot is empty, just to make sure I use the right card, but I'm not certain I'm using the correct file.