It seems that this issue is always coming up, so I am going to make a thread which I can add to the READ FIRST thread, to keep track of it and can search for it easily.
Member Vic7767 has taken some of theses pictures, which we greatly appreciate. I am just placing them in a single thread to make it easier to search.
First, remove the bottom plate, and remove the 4 screws holding the CHM in place (Noted by the red circles):

Next, turn the CHM over and see if there is any hair/debris needing to be removed:

Next, this .gif shows you how to get to the gears inside the CHM:
Hopefully, your CHM won't look like this!
If it does, now is the time to clean the junk out, re-grease the gears, and close it back up. If you are still under warranty, I would call iRobot to have them ship you our a newly designed CHM, which will help keep the debris out of the inside. If your warranty has expired, PM member Vic7767. He can modify your CHM with bearings to prevent this from happening again.