Folks are evidently downloading and installing Aperture 3.3. How? I'm running 10.7.4, and Software Update installed iPhoto 9.3 and iTunes 10.6.4 on my system. But nothing about Aperture, which is currently at version 3.2.4.
Have you moved or renemed Aperture from being simply that and at the root level of the Applications folder?
Software Update worked nicely here. Compare your spec to:
One of the following Intel-based Mac computers with Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor