Currently Being ModeratedJan 27, 2013 11:24 PM (in response to KKlinda)
First thing to do is figure out if your iPhoto program is working properly. Do you have another user on your computer you can log in as? If so, do that and see if that user can work with photos within iPhoto (with a different iPhoto Library than the one you've been using). If it seems to work without the problems you've been seeing, then go to Step 2 below. If you don't have a second user you can log in as, you can create one, or if you prefer not to do that, simply start iPhoto holding down the option key and create a new iPhoto Library. You can then test that new Library by importing a few photos and working a little while with them. Assuming the program works properly in either case, go to Step 2. (FYI, you can switch back to your old Library again by restarting iPhoto with the option key held down.)
Step 2. Once you ascertain that the iPhoto program is working ok, it would then seem likely that a faulty iPhoto Library is cauing the trouble. Since you already rebuilt the Library from Apple's instructions, you should try a stronger type of rebuild of the Library, using iPhoto Library Manager. You can download this program for free, but not all its features are available until you pay a small fee. However I think that the Library rebuild feature is available in the free version (not 100% sure about that). When iPhoto Library Manager rebuilds your Library, it does so by leaving the original file untouched and it creates a new Library that it creates from your photo files plus the data about them. So you can always revert back to the original file if need be. (That is not the case with the Apple-provided rebuild feature.)
Hopefully Step 2 will fix your problems.
If Step 2 does not work for you, then you may have to import your original photos into a brand new Library, or maybe reinstall iPhoto. These are more complex steps and might be best to wait to see whether Step 2 works for you.