Usually the humming/buzzing sound means that the ceiling fan is still receiving power but it's not transmitting that power through to make the ceiling fan spin, which usually are either of two scenarios:
1) If you have a ceiling fan that has pullchain, and are using a remote control, in-wall remote, in-wall switch, or any other wireless device to control the speed of your fan, it is very possible that the speeds may be mismatched. To fix this make sure to set press/set the speed on the remote you are using to high. Then go to your ceiling fan try pulling the chain and see if the highest velocity is matching to the setting you are on. Once you get to that point go back to your remote and test all other velocities. After that the humming/buzzing should be gone.
-or-
2) A bad capacitor. These pieces are sometimes vulnerable to power surges and they can go bad over time. You can purchase one of these capacitors from any of our models or if you are looking from another brand that is not ours you can always give us a call an see if we can provide you with one that will fit your current fan.