iPhoto update issues

My MacBook is telling me that I have to update iPhoto, but when I try update it it says something along the lines of "you can not update because you have not owned the major version of this software" and takes me to the app store, or at least asks me to sign in. When I sign in it just says that there is an error 100 with the app store, but I can access it though the app store app on the dock.

any ideas??

Thanks.