HT3805: Aperture 3: Troubleshooting BasicsLearn about Aperture 3: Troubleshooting Basics
Have a look at my User Tip: If Aperture is unresponsive, how to avoid force quitting?
If the terminal command does not work, repair your Aperture Library after Force-quitting, if necesary, rebuild.
When you start Aperture the next time, hold down the Shift key to defer the generation of previews. If that succeeds, report back.
Do you have a working backup of your library? If not, back up before rebuilding.