When trying to edit a photo, it disappears (black screen) or screen is full of lines. Is this a bug with the latest software update?

Well if it is a bug then only you have reported it

Have you rebooted? DOes this happen with every edit? Or only some? If you exit edit mode and then come back do you see the same thing? Any display issues with any other program?

LN

There are several possible causes for the Black Screen issue

1. Permissions in the Library: 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. Include the option to check and repair permissions.

2. Minor Database corruption: 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.

3. A Damaged Photo: Select one of the affected photos in the iPhoto Window and right click on it. From the resulting menu select 'Show File (or 'Show Original File' if that's available). (On iPhoto 11 this option is under the File -> Reveal in Finder.) Will the file open in Preview? If not then the file is damaged. Time to restore from your back up.

4. A corrupted iPhoto Cache: Trash the com.apple.iPhoto folder from HD/Users/Your Name/ Library/ Caches...

5. A corrupted preference file: Trash the com.apple.iPhoto.plist file from the HD/Users/ Your Name / library / preferences folder. (Remember you'll need to reset your User options afterwards. These include minor settings like the window colour and so on. Note: If you've moved your library you'll need to point iPhoto at it again.)

If none of these help: As a Test:

Hold down the option (or alt) key key and launch iPhoto. From the resulting menu select 'Create Library'

Import a few pics into this new, blank library. Is the Problem repeated there?