I'm having the same problem, it sounds like. I've followed every direction I could find on this site - using the new client, the patched client, trying an update, not trying an update, trying different setup options and I am able to create my character and right after that process the client crashes. When I open it back up I can log in and click on my new character, but as soon as it tries to connect, the client crashes. I've tried running it from the command line - as root and as an admin user, as well as from the GUI.
I'm on a brand new Intel Macbook Pro in OS 10.4.10