iphoto not working on OS X Mountain Lion

Never done this on Mountain Lion....but try this:

1: use spotlight to see if it just got moved somewhere else for some reason.

2: If you still can't find it browse to the app then you should be able to restore it from TM.

Read the steps here for ML: http://support.apple.com/kb/PH11103

or reference this thread:https://forums.macrumors.com/threads/1222657/

If you erased your hard drive to upgrade to ML, and now you are missing the iLife apps, which includes iPhoto - you should be successful in restoring iPhoto from your Time Machine backup, following the tips that tampasteve offered.

If that doesn't work, you can reinstall the iLife software from your original installer DVDs. That's the set of two grey DVDs that came in the box when it was new. The 2nd disk is the one that you will need.
If those are gone, or lost, then you will need to find a reinstall disk for iLife '09. And, it's also possible that iPhoto 8.1.2 won't work with Mountain Lion, and you really will need to update iPhoto (which means purchasing iLife '11) - but, you can also get the latest iPhoto by itself at the App Store (which also means upgrading to Mavericks)