Paul, moisture problems are tough. But in colorado the air is usually dry except this is a weird weather year so who knows. When the temperature hits the dew point temperature, then condensation occurs.
Your insulation sounds inadequate. If the 4" is loose fill with no vapor barrier, then that may be how you are getting excess moisture up there.
Maybe sweep up the loose stuff one area at at time, place some fiberglass batt insulation with the kraft paper vapor barrier face down towards the ceiling and then overlay with loose stuff to fill in joist cavities, etc. till you get to an r-38 or r-30.