Have your chimney inspected. It sounds like it has a crack and moisture leaking through.
You are wasting your time cleaning and painting until you find the source of the leak.

Other possiblity is that you have a pipe vent from a bathroom near by and with all the rain the pipe collection site for rain water that is there has overfilled from all the recent rain and the water dripped down into the ceiling and wall.
I say this cause it just happened to us this past week. DH did a quick fix with a rag and a large bucket. He tied the rag where it was dripping and had the rag hang into the bucket. Water follows the rag drips into bucket.

The other poster is right it could be the area around your chimmney. Flashing could be coming off or gone. Shingles could have peeled back some due to age, mortar around the bricks could have flaked off and changed the flow so now you get water. It could be any one of those things or any combo of them.

Hiding I don't think a good idea. No matter how upset it makes him it will make him more upset if it was a simple fix and by not telling him you allow it to get worse.

What kind of fuel do you have? Is it weepy? Like rain, or is it just moist? If it's weepy and it's elsewhere and NOT in the attic, and you burn gas or oil I would STRONGLY recommend that you have your chimney checked to be sure it's not plugged and it's not CO2. I don't want to be an alarmist, but I know from personal and professional experience that plugged chimneys are very, very serious.

THIS IS CRITICAL IF YOU HAVE YOUNG CHILDREN (even if you don't!)!

Having said that, if it's flashing, then although not deadly, not paying to have it fixed now will only compound in the future.

Obviously we will have to have any problems fixed. Whatever it turns out to be.
We have a carbon monoxide detector about one foot from this area. I check the batteries every two days. Would the detector pick up the problem if it were CO2? Most of the spots/moisture trails have dried up at this point. Only the end of the trails are tacky (like oil, or adhesive?). Most of the spots are prety far from the chimney--on opposite walls a few feet-say 7 feet away. The spots on the ceiling seem to be around a pre-existing crack. I have been priming this area a few days before. Could the paint have failed in some places and wept? Something like this happened when I painted some woodwork that wasn't as clean as I had thought.
Oh my goodness, now I am really freaking out about the CO2. Should I call a chimney guy asap?

We had exactly the same situation with dark spots on the ceiling. After having several great handyman types look at it, the concensous was it was poor ceiling insulation. We had new ceiling insulation blown in and it hasn't happened since. I had the ceiling painted and it's still pristine after about 4 years (no more dark spots).

Sorry about the grumpy husband...I just fix things or get them fixed and let him know it's for his own good:). Good luck!

Didn't you say you just had the furnace looked at? Why not call the guy back and just ask him on the phone whether or not he thinks there was a problem w/ the chimney. 'Course, he should've noted that as he was working on it, if there was a problem....

Yes, the CO2 detector should pick up the problem. If the problem is drying up, perhaps it is the paint. Can you look at the chimney yourself?

If you had a new furnace,is it high efficiency? They sometimes create more humidity in the house. Check humidity level. Also make sure your attic has enough roof vents, could cause a humid condition. Also make sure no exhaust vents are venting in the attic, that they are vented through the roof, check kitchen stove vent, bathroom vents etc.

Some homes need a power vent with a humistat on it to automatically move humid air out of the attic. The electric and gas companies have a formula for how many roof vents you need per 1000 sqare feet. If you have an older home with an old roof you may need more vents.

If your house is to air tight you may need an air exchanger. Just a few of my thoughts hope it helps.

Might I suggest you have a small and quiet talk first with your children... you are saying that it's wet but perhaps oily or sticky? See if the kids got into anything that they might have shot up on the ceiling. I can think of more than a few things that are ina can that kids could shoot at the ceiling and leave a real mess. But that might be because last week I went it to find the kids bathroom ceiling dripping with shaving cream blobs.... one of these days having 5 kids is going to kill me ;-)

Maddiemom

Never put an attic fan in your home. It's the worst thing you can do. If your ceiling inside the house is properly sealed and insulated you have no worries. Your attic air should be very similar to the outdoor temperature. If the house is changing the attic air than you must find the leak first. If you add an attic fan it will pull your heated or cooled air from inside the controlled environment to the attic. If there is nowhere to compensate the fans pull of air. It will literally pull the air from the earth right through your concrete blocks and floor in the basement. Now Radon comes into play. So please have an audit done on your home. It will be the best money spent!!!!!

I second the energy audit idea. Super way to invest in your home.

Whatever it was has not happened again, Although the heat has been on since then and we had very heavy rain. I am tending to think that it was failed paint. All the responses helped me to think about really important potential problems that I had not even considered. I really appreciate all the ideas that you came up with. My husband noticed it the dsy it happened too, but since he works at night, we didn't discuss it for a few days. We are both watching the spot!

Attic fans are great. Had a moisture problem in one house and it cleared up the problem. First of all it only runs if the humidity is to high. It's adjustable. Second it very rarely runs and only when it needs to. Also my attic has the proper amount of vents and soffit vents, so it can and will take the air from the easiest source. Solved my problem immediately.

I had a house full of girls, when getting ready for school I had two showers going at once. Btw all my bathrooms had exhaust vents going to the outside. My wife cooks alot, and yes we had a down draft range vented to the outside.

I could see a light brown area around where the ceiling meets the outside walls. My roof had some springie plywood in it. So I tore off the roof and replaced the bad wood. So that was my concern when I installed the power vent. It was expensive and I didn't want that to happen again. Also this vent has a thermostat on it that cools the attic in summer.

Just my experience. BTW it's been good for 15 years since the fan was added.