and it may be too late to catch you given the time difference, do the following.
Go to the top right hand corner of the screen, where the little magnifying glass is and click it.
Type in iPhoto and see what you get.
The ? mark on the dock means that the alias cannot find the original. You can get this effect if you move an application from one folder to another. The alias looses track of it.
Ditto for System Preferences.