IPhoto always becomes unresponsive

Question

Every time I use iPhoto, my computer (Macbook Pro 2011) freezes (all programs become unresponsive) and the fans become very loud. I lose whatever I changed in that session each time. At best, iPhoto is just very slow with the rainbow pinwheel happening often, and I can't have music playing in iTunes at the same time.
Does anyone know why this happens?

Answer 1

Damaged Library.
Back to the original Library then
Option 1
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:
Option 2
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.  
Regards
TD