Sounds like you've picked up some malware. As soon as you get rid of it, the functionality should return to normal.
I haven't been able to find help for this anywhere. It's been over a week since I reported the problem to facebook's support team, and they have not e-mailed me back.
When I search for a person on facebook now, I no longer get the "filter search" sidebar on the left, along with a list of people. It's just a bunch of spam now, a lot of bing web results and sponsored results.
Please help! Thanks in advance