When editing a document in Word, I have a problem with replacing text
that I have selected. For example. If I have a sentence that reads:

The quick brown fox jumps over the fence.

Let's say I want to replace the word brown with black. I would
highlight the word brown and then just start typing 'black.' This
should delete the word brown or any text I have highlighted, and replace
it with what I am typing on the keyboard. It does not do this. It will
type the word in right next to the highlighted text resulting in the
following:

The quick blackbrown fox jumps over the fence.

Any suggestions as to why this might be happening?

Thanks,

Dave