Does it crash during the rebuild or after the rebuild when you are running Aperture?
If it is after the rebuild when you are running Aperture try pressing the shift key as soon as you start Aperture. This will prevent preview generation. If there is a corrupted image in the library this should allow Aperture to run. If this works then we;ll need to hunt down the corrupted image.
Post back the results.
Deleting those images from Aperture should let you get Aperture running normally again.
Once you delete them in Aperture and empty the Aperture trash they will be put in your system trash. If they are images you might want to try and rescue I would recommend taking them out of the system trash and putting them somewhere, say your desktop.
Then you can try opening them in say Preview to see what happens and what they look like. Depending on what Preview does it my be possible to save them.