Trichardlin, I thank you for your input, which I'm sure would have been helpful to a savvy user.
I finally took my iMac to Best Buy for their "experts" to have a look and after half an hour of research and investigation they too surmised that my best alternative was to delete Aperture and re-install it. Luckily, before I undertook this task, a neighbor kid, 14y/o, heard me complaining to his Father about my love/hate relationship to computers and offered, "your hard drive is probably full." End of story.