Nice profile pic Steve! We have to update the forum software from time to time for security purposes, adding new features (such as the "new" photo gallery that you all see now) and new functionality. A few things to keep in mind:
Make sure you clear all cookies originating from koi-bito should you have problems.
Always access using "http://www.koi-bito.com/forum/" rather than "http://koi-bito.com" as we have some rewrite rules set on our server that will try and redirect you to "www." anyway. I suspect this may be the source of the problem that some of you are facing.
You'll notice some more changes as we go into summer, none of which should affect your access so long as you use the "www." prefix.