Leopard Locks Up with Places

I have had the lock up problems that many have complained about here. On my 2006 Intel 20" iMac with an external Firewire drive, I think I have found what causes it. In Finder, I drag 8-10 directories to the "Places" sidebar for easy access. When Finder crashes, I lose the directories. I was routinely replacing them, but the last time it locked up (endless beachball), I did NOT re-create the directories. I have not had a lock-up since. It is not as convenient to use without these shortcuts, but I think the lock-up problems are related to this docking of directories.