100mm L 2.8 macro lens

I know this sounds basic, but just a few things to double-check:

1. Make sure you don't have the 2-second timer set. I sometimes use it when doing macro work on a tripod and then forget to turn it off.
2. Make sure the exposure is not locked (*).
3. Make sure the mode dial is clicked properly and locked into one of the modes (P, Tv, Av, M, B).

(Ask me how I know these.)

Good luck.

Mine has never buzzed either, it knew the words right from the beginning.

the only noise i hear from mine is the IS motor. overall it's fairly quiet.