Please post more information. We barely have enough to even begin troubleshooting.
Do you get any error messages when the quitting happens? Does it happen to all applications, or a subset? Does it happen randomly, or when you perform a specific action?
How did you install 10.4.11, and what version were you upgrading from? Did you simply update from 10.4.10 to 10.4.11, or were you previously on 10.3? If so, did you do an Upgrade Install? Archive and Install? Clean Install?