As most people here, I've had Aperture crashing at startup after the 3.4 upgrade.
Removing the preferences file works (~/Library/Preferences/com.apple.Aperture.plist) , but Aperture will crash again at startup as soon as you restore your Facebook account.
I did a full re-install, restored the FB account, and Aperture was still running. However, trying to view Facebook albums or synchronising them made Aperture crash again, with the backtrace indicating a Facebook query.
Am I the only one seeing this ?
For the record, yesterday's update 3.4.1 solved the problem. No more crashes (at least not with Facebook integration).