iPhoto "A photo Has been found in the iPhoto library that was not imported"
Open your iPhoto Library package by Control-clicking on it and selecting "Show Package Contents" from the contextual menu. Look for a folder titled "Importing" or "Import" (NOT Auto Import") and see if it has any photos in it. If it does move it to the Desktop (do not move or rename any other folder/file while in there). Launch iPhoto and the message should be gone.

Check that folder to see if the photos are any you don't have in the library or want. If not, then delete. If so, import again.