This is not a bug, it's a "feature" that's here to "help" you to find stuff you want more efficiently. :roll:
At least that's what Jason has said time and time again. Unfortunately for him, his new search (which was originally the only option) has never found me anything I wanted, and in fact only made searching so much harder that I wished I never had to look for anything again. When enough people (read: anyone that ever searched for anything after the "upgrade" and knew about our "Forum Issues" section) bitched about it, he finally had to give in and put back the sort-by-date search. The default is still the "relevancy" (how the results are relevant never was obvious to me) search, but you can find the checkmark to enable date sorting under the search page.