iphoto 08 question

When i click on my photos in iphoto I get the dreaded black screen with the question mark!!! Which I know means my files can't be found. But what's weird, is the files are on my computer, and can be found in the finder under photos/iphoto library. When i drag them into iphoto, the caption comes up saying that it cannot add photos because photos already exist. How is that possible? Why is it that I can only view the thumbnails and not the actual files? Of course, some of these are actually important pictures.

Any ideas would be great!

You need to delete the one ones that come up with question marks and then reimport them. iPhoto doesn't like it when you move photos around outside of the iPhoto program.