I suspect that the presence or absence of the Search Box in the upper right hand corner depends on how the person got here, i.e. using what URL - which would presumably depend on the place they found the link to DT, and whether it was the most recent version or not.
(For no particular reason, I have kept several of my older bookmarks to the discussion forum, as well as the newest one ... I kept thinking I should delete the old ones, but never got around to it, & now am glad that I didn't, so that I can prove my point!)
So for example, at http://www.onstagemedia.com/cgi-shl/dbml.exe?Template=threads.dbm&Title=&Age=30 I do get all the current threads, but there is NO search box, NO link to the new Forum Search, & a somewhat less fancy layout overall.
Whereas at http://www.onstagemedia.com/mudcat/threads.cfm?Title=&Age=30 I get the newer layout, complete with search box & link to Forum Search.
Lastly http://www.onstagemedia.com/mudcat/threads.cfm?Title=&Age=3 is the most recent link provided from the home page, it differs from the one just above only in that the default age is set to 3 (days) rather than to 30.
Perhaps the Site Managers should either provide a link from the old address to the new one "Click HERE to get our new format" - or replace the old site with a message "We have moved to ... " so that newcomers who find the site via links that have not been updated, will nevertheless end up on the newest version of the Discussion Forum. (Ah, always one more thing to do ... )