Aperture will no longer open on my Mac Book Pro with operating system OS X 10.9.1 (13B42). When I try to open it it just says, "Aperture can not be opened while it is being updated."
What version of Aperture are you using?
If you got it from the Mac App Store, try deleting it and re-installing it by re-downloading from the App Store.
Also: Consider running Software Update and updating to 10.9.3.
Retrieving data ...