then I imported more photos this afternoon.
You may have imported a corrupted image o video. Hold down the "Shift" key, while you double click Aperture to launch. This way Aperture will open with out trying to process the newly imported images. If that succeeds, export the originals you imported last, to safe them and delete them from the library. Then check them outside Aperture, if they are o.k. (with Preview, or another photo editor).
If you cannot get Aperture to launch with the shift-key, post a crash log. (the first 50 lines)
crashes immediately regardless of my attempt at repairing permissions or the library.
Did a repair succeed at all? If you can get Aperture to launch with the Shift-key, try the repair/rebuild first.
I am running 10.6.8, 2.66 GHz, with 6 GB and 4MB of RAM.
How much disk space do you really have? How much is free? And do you mean 4GB of RAM?