I don't understand how to do some of the things you have said so I will continue to learn as I go along.....Ta!
That's essentially what we all do here: there is a puzzle (like your problem), and we're trying to figure out what's going on.
The question is: where do you start? Without going into great detail right now, Artie's suggestion represents a standard troubleshooting approach. The general idea of testing something in a fresh user account is that you start there with
default settings. Quite frequently computer problems are caused by incorrect or corrupted settings of one or more programs, and such settings are user-specific. You can eliminate (or confirm) this possibility by testing if a clean user account also suffers from the problem.
If the problem persists there, that would indicate that it is at a higher, non-user dependent level, and that includes applications and the System itself.
If the problem is restricted to one user account, it tends to be associated with a corrupted preference ('.plist' file) or cache there, and the question then becomes which one(s).
Assuming your Guest account was clean (I don't know if it was used previously), your test result suggests we're dealing with option 1: an issue with an app (iPhoto) or the System.
