I have been using a new Nikon camera since July. The videos that I downloaded to Iphoto have been great except those that have been taken since Sept. 5. They are slightly jerky. I did not change any settings on my camera. I took it back to the shop and had them checked. I downloaded the videos on Quicktime on my son's computer (which is not an Apple product) and they worked. I can play them on the VLC Media player on my Power Mac G5. They just don't work on QuickTime on my computer. The Apple technician suggested that I post this message for help from the experts out there.