I commonly switch between metric and imperial when drawing dimensions, however recently when typing the "C" for "cm", only the m appears.
I'm sure I've accidentally disabled something!
For example, If I am in an imperial setup, and go to type in 10cm, it normally converts it to 3.937", however now it misses the "C" so I would type in 10m, and it would end up being 32'9.701"