YOu haven't really given us enough information to help you. (We don't know what operating system you're using, how fast your processor is, etc.).
But to start with, have you resized your photos to no larger than 1000x750 pixels, as I recommend in my books in and in our FAQs to the right of this forum?
This is aimed at Premiere Pro, but may help
Work through all of the steps (ideas) listed at http://ppro.wikia.com/wiki/Troubleshooting
If your problem isn't fixed after you follow all of the steps, report back with ALL OF THE DETAILS asked for in the FINALLY section, the questions at the end of the troubleshooting link... most especially the codec used... see Question 1
When you say "pictures," I immediately think about still images. Is that what you have?
If so, what are the pixel x pixel dimensions of these?
This ARTICLE will give you some background on still images.