Oddly enough, dreaming of a coworker rarely involves issues with work itself. The focus is more likely to be on traits this person possesses that mean something to you. (For example, if this person's voice is especially loud, whatever he or she is saying to you in the dream is especially significant, and you should pay attention. If this person is someone you feel you can trust, there is some issue in your life involving trust that needs to be resolved.)
Basically meaning, that the attributes of these people is something you identify with as part of your own personality. It's your subconscious playing out your fears, likes, dislikes, ideas, emotions, urges, etc ...but using people you are familiar with, as the actors.
The coworker falling could be acting out a fear you have, such as falling down...especially if you're a server, or bus person, of any type.
Sex with the other coworker is a way of exploring possibilities of your sexual urges without testing them in your waking life.
Hope this gives you something to go on, Best of Luck!