A strong warning: If you're trying to edit the Library (that is, make albums, move photos around, keyword, make books or slideshows etc.) or edit individual photos in it via Wireless be very careful. Dropouts are a common fact of wireless networking, and should one occur while the app is writing to the database then your Library will be damaged. Simply, I would not do this with my Libraries.
As to the issue:
What version of iPhoto? Assuming 09 or later:
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 Repair Database. If that doesn't help, then try again, this time using Rebuild Database.
If that fails:
Download iPhoto Library Manager and use its rebuild function. (In early versions of Library Manager it's the File -> Rebuild command. In later versions it's under the Library menu.)
This will create an entirely new library. It will then copy (or try to) your photos and all the associated metadata and versions to this new Library, and arrange it as close as it can to what you had in the damaged Library. It does this based on information it finds in the iPhoto sharing mechanism - but that means that things not shared won't be there, so no slideshows, books or calendars, for instance - but it should get all your events, albums and keywords, faces and places 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.