This sound like a phenomenon that we used to call "blushing" Testing showed that moisture (good old H2O) was seeping into the coating and bonding with some of the fillers in the coating that have a lot of sites in their molecules for hydrogen bonds (water loves these!). The end result was the white haze or "blush". This is a totally reversible situation and can be eliminated by baking the board for about 20 minutes at 250 deg F (you drive out the moisture and away goes the blush). You may want to consider giving your assembled boards a drying step (say 20 minutes at 250 deg F) before you apply the conformal coating because the moisture may be coming from the inside, not the outside. Its worth a try! Hope this helps. Larry Fisher Allen Woods & Associates