I have, all of a sudden, multiple already imported photos that are visible in thumbnails but not in the main viewer.
Instead, the main viewing screen shows only a large exclamation mark in a double triangle this is in an otherwise black screen.
iPhoto '11 version 9.2.1, running OS 10.7.3, MacBook Air 1.8 GHz Intel Core i7, 4 GB 1333MHz DDR3,
Is it repairable?
This, by the way, happened soon after the import and before my usually scheduled back up.
Therefore, no backup for these photos
Also, where is the iPhoto Library?
The ! turns up when iPhoto loses the connection between the thumbnail in the iPhoto Window and the file it represents.
The iPhoto Library is in your Pictures Folder.
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. .