pc sees ipod content, but content doesn't show up when disconnected

I dragged my new photos (from my pc desktop) into my Ipod Nano 4th gen; while connected to the PC the new content shows up, but when I unplug the Ipod, none of the new photos show up. I even tried dragging the new folder into one which does show up. It didn't work. This also happened when I dragged some music into the Ipod... showed up while connected, but not when unconnected from PC. How do I get the content to show up, and work on Ipod? I have over 5gig unused memory, so that should't be an issue. Thanks for any help.