Thanks for all the replies. I guess I need to clarify.
My router is setup to use DynDNS and works like a charm. It's always on.
My PowerBook is connected via 802.11 to my wireless router, which is
attached to the main router. My PowerBook has a fixed IP address with the
wireless router. The main router uses my wireless router as a DNZ, so all
traffic goes to my wireless router, which then routes the appropriate
ports to my PowerBook. All this has worked without a hitch. The problem
with running DynDNS on the PowerBook itself is that the PowerBook reports
its private IP address. I once used a program which determined the
machine's public IP by visiting a website and recording the IP as seen by
the site, but this program seemed to run only upon login.
The problem seems to be that, upon reboot, the PowerBook does not
establish contact with the wireless router until there's been a login
event. Being paranoid, I'm not thrilled with setting my PowerBook to log
into my account automatically, especially when I'm not there.
Any further advice would also be greatly appreciated.