Back Up and try rebuild the library: hold down the command and option (or alt) keys while launching iPhoto. Use the resulting dialogue to rebuild. Choose to Rebuild iPhoto Library Database from automatic backup.
If that fails:
Download iPhoto Library Manager and use its rebuild function. This will create a new library based on data in the albumdata.xml file. Not everything will be brought over - no slideshows, books or calendars, for instance - but it should get all your albums and keywords back.
Because this process creates an entirely new library and leaves your old one untouched, it is non-destructive, and if you're not happy with the results you can simply return to your old one. .
There are 9 different versions of iPhoto and they run on 9 different versions of the Operating System. The tricks and tips for dealing with issues vary depending on the version of iPhoto and the version of the OS. So to get help you need to give as much information as you can. Include things like:
- What version of iPhoto.
- What version of the Operating System.
- Details. As full a description of the problem as you can. For example, if you have a problem with exporting, then explain by describing how you are trying to export, and so on.
- History: Is this going on long? Has anything been installed or deleted? - Are there error messages?
- What steps have you tried already to solve the issue.
- Anything unusual about your set up? Or how you use iPhoto?
Anything else you can think of that might help someone understand the problem you have.