You are not alone, this happens to me all the time.
However, only if you dictate that word alone, not within a context with other words. If you dictate the word "no" alone (or with a pause) in the Encounter window, it will drop down the "Know" menu from the top of the window. If you dictate it as "no period" it will correctly type "no."
My observation is that the Dragon speech engine is very accurate within the context of a sentence. Less so with single words.
