Video Stutters

I just took a bunch of photos and videos, and the videos aren't playing back smoothly. It's similar to what the images do in a flip book when you flip the pages. I know it isn't the camera, as the video plays back fine on the camera itself. Also, when viewing the photos as a slide show, the dissolve from one photo to the next isn't smooth either - when going from one photo to the next, the dissolve will hesitate, and then suddenly resume with the next photo, rather than there being a smooth, gradual transition. This is a recent problem, I haven't had any issues with video or the slide show until now. I'm not sure what may have changed. Any ideas what I can do to fix this? Any help would be much appreciated. Thanks!