Originally posted by ripit thanks for all the advise. I blew inside the camera (towards the roof which I guess is the focusing screen). The camera has been inside for weeks before and days after this. I mainly use it for family photos right now (I have young children and don't have a lot of tie for leisure shooting right now).
I double checked the viewfinder on the outside (cleaned it with dry cloth) and that doesn't seem to be it. It does seem to be going away a bit on its own over time though. I can probably dig up some silica gel packets at work (not for a few days though). Do i put it with them and the lens on, or lens off? Can water evaporate out of the camera with the lens on? I assume off would be better but worry about dust or further contaminants.
Come to think of it, are body caps vented on the sides or do they seal?
Well, if it's going away, it's pretty surely got to be moisture of some kind. Probably the best way to deal with it would be to put the camera, without lens and body cap, in a box with some dessicant (or like a bag of Minute Rice made of some permeable cloth.) I wonder if it could possibly have gotten into the pentamirror, if it's been taking so long to clear.