After hours on the phone with Apple tech support over the past few days, my SL issues (apps repeatedly crashing) have been resolved. It seems the problem was that I upgraded. The original SL install DVD I bought was defective and corrupted my hard drive. Even though I exchanged the DVD and reinstalled, from that point on I was upgrading a corrupt system. The Apple tech walked me through using disc utility on the DVD to wipe the system hard drive, repartition it and install a virgin copy of SL. What a difference! The install took about 20 minutes instead of nearly an hour. And all my apps now are blazingly fast. The tech advised me NOT to use Time Machine to recover all my files and settings, but to manually drag over what I need. So far so good. It was a pain, but if the system is finally stable, I'm happy.