Hello Old Toad thank you for responding.
I attempted to rebuild the library, by holding down the alt and command keys whilst opening iphoto, and I have now found that whatever options I select, I get this message:
Your photo library will not be readable by previous versions of iPhoto after the upgrade. The upgrade process may take several minutes depending on the number of photos in the library.
I select 'upgrade' and I get this message:
You have made changes to your photo library using a newer version of iPhoto. Please quit and use the latest version of iPhoto.
I have done nothing to iphoto and now it seems that it will not let me do anything to it
Any other ideas will be very much appreciated, thank you, Jenny