Can anyone tell me what on earth is wrong with iPhoto

It does look like a software (or graphics card) issue. I would suggest making sure you have a backup of the iPhoto library (in case further corruption occures) and re-downloading iPhoto from the Mac App Store (you'll need to delete the app first).

If you already tried all this, then the issue is likely to be a corrupt photo library.

Make a backup; download iPhoto Library Manager; run its library rebuilding function (this is actually non-destructive, as it creates a new library, but a separate backup is still a good idea).

http://www.fatcatsoftware.com/iplm/

Try this: make a temporary, backup copy (if you don't already have a backup copy) of the library and do the following:

1 - delete the iPhoto preference file, com.apple.iPhoto.plist, that resides in your

User/Home()/Library/ Preferences folder.

2 - delete iPhoto's cache file, Cache.db, that is located in your

User/Home()/Library/Caches/com.apple.iPhoto folder.

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3 - launch iPhoto and try again.

NOTE: If you're moved your library from its default location in your Home/Pictures folder you will have to point iPhoto to its new location when you next open iPhoto by holding down the Option key when launching iPhoto. You'll also have to reset the iPhoto's various preferences.

I'm skeptical the above will help since trying iPhoto in a new user account would essentially do the same thing.

If that doesn't help boot into Safe Mode and try iPhoto again. If iPhoto performs correctly in Safe Mode then reboot and try again. If it still is messed up I think there maybe something wrong with some system components..

If iPhoto performs the same in Safe Mode then it's probably hardware related since you've reinstalled the system and iPhoto. Take it to an Apple store and have them look at it.

OT

iPhoto '11 does not perform correctly on my Mac Pro 2.8 Quad-Core running OS 10.7.3.

I upgraded to iPhoto '11 via the App Store. Since then whenever I play a slideshow, the line of thumbnails at the bottom of the screen no longer pops up no matter what I do. I deleted the app and also deleted all the files containing com.apple.pkg.iPhoto. Then I reinstalled iPhoto '11 from the App Store. Rather than use an existing library that might be corrupted, I just located some jpegs dragged them into iPhoto 11 and created a new iPhoto Library. The problem persists. It is not intermittent.

I also installed iPhoto '11 on my Intel (not Core 2 Duo) Macbook Pro laptop. It is loaded with the latest version of Snow Leopard. The thumbnails appear just as they should, allowing me to quickly jump to different points in the slide show.

I am at a loss as to what to try next.

Doug

It sounds like it's a software/system issue. You've done all of the potential fixes that I can think of. Maybe delete iPhoto and reinstall it one more time. To do so you'll have to delete the current application and all files with "iPhoto" in the file name with either a .PKG or .BOM extension that reside in the HD/Library/Receipts folder and from the /var/db/receipts/ folder,

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Then install iPhoto from the disk it came on originally. Then try iPhoto before applying any updaters.

Thanks you very much for taking the time to consider my issue. Folks like you are what makes the Apple community the best.

iPhoto 9.3 is now out, still having the same issue? if so, try disabling any unneeded quicktime components