Afterthoughts, too late to edit my post above: strip the resource forks out of the files
after exporting them from iPhoto to a folder on the desktop, and
before copying them to the SD card.
GraphicConverter
Drag the folder full of pictures onto GraphicConverter's icon to open an image-browsing window in GC. Type Command-A to select all the thumbnails in the window, click the "Other" icon in the toolbar, and find the *Remove Resource Fork* command in the extremely long drop-down menu that will appear. This will strip the resource forks out of all the files at once. Quit GC and copy the photos from the folder onto your SD card, and test again on your TV.
GC is one of the all-time great values in Mac software, packing near-Photoshop power at 1/20 of Photoshop's price. I highly recommend paying for it and learning some of its hundreds of amazing capabilities.
Message was edited by: eww