Brian,

Sounds like a corrupt preference file. But before trashing Aperture’s preferences, try this. With your camera connected, launch Image Capture. Select the camera in the list, and a the bottom left of the window, you’ll see “connecting this <device> opens:” and a drop-down menu. Set that to Aperture, and see if that solves the problem. (If you don’t see this option, click the tiny black box with a triangle in it in the very bottom left corner).

If that doesn’t do it, try trashing the Aperture preferences (see the FAQ if you’re not familiar with how).