This Friday (23rd) at about 10am GMT, the boards will be taken down for a search index update, which will last a couple of hours, at least. This will fix all the invalid threads coming up when you do a search and find a thread which was moved out of the forum it has been posted in originally. This is not fixed automatically and is one of the limitations of UBB, so the search indexes for all forums have to be updated every now and then, especially with the amount of threads moved around from the SoA to the ToB forum.