A while ago, I read on the Tech Board that the search function is disabled when traffic to the boards is high to keep things from getting to slow. During off-peak times you should be able to use it.
That was also talked about in the Tech Baord. The message is a canned message built into vBulliten (the format for the DIS boards) and can't be changed by the webmasters.
When the DIS goes to the newest version of vBulliten later this year, there should be more acceassibility to the software by the webmasters.