How do I get Emacs to interpret M-left as previous word?

Question

I'm very used to having Emacs interpret M-left/M-right as backword/forwards word. However, last night, for some reason, Emacs started interpreting M-left as D and M-right as C.

I'm wondering how I can restore the default behavior. I haven't changed my .emacs file at all, and I'm using iTerm, with the option key set as meta.

Any help will be appreciated.

Thanks!

--Edit--

I've figured out that the problem is with iTerm and not Emacs. Emacs interprets the commands correctly in the built-in terminal, but not in emacs.