Is this the first time you're launching iPhoto? Did you just purchase this computer? If so, check if there's a software update to bring it to version 8.1. If its running 8.1 or you were able to open iPhoto before to import images and you have a library already there, try creating a new library to see if iPhoto is taking issue with your library. To create a temp library, hold option while launching iPhoto, select the option to "Create New" and save the library in ~/Pictures. Does iPhoto open? If not, dvdhsu's recommendation has merit. However to avoid complications with the reinstall process, removing the iPhoto application from /Applications and receipts related to iPhoto from /Library/Receipts is not a bad idea. As dvdhsu posted, insert the second disc, launch the Bundled Applications installer, and customize it to put just iPhoto back on the system.
