Mysterious Wall Problem

A really bizarre thing is going on with our wall. I was all set to post a photo and say "what on earth can it be?" Now, I need help it figuring out possible causes.

This is a section of our bedroom wall. Behind the wall is a chimney (that vents our boilers). The wall itself is plaster, with a skim coat of compound on top, followed by latex paint. (The plaster had a mixture of paint on it as well, oil and the like).

As you can see from the photo, it appears that moisture is in the wall, and is collecting at the "bubble" points. (this is the photo from this morning)


The "water" issue starts at the picture molding and works it's way down. There are no other apparent areas anywhere else on the wall.

The cosmetic fix is easy-relieve pressure, let the water out, scrape, patch and paint. But, more troubling is if water is getting in, where is it coming from, and how can we stop it from coming in?

Of course, all this is happening in our one finished room which doesn't make us remotely happy. Our bedroom to boot.

Oh, an another fact for anyone who didn't read the "unfreezing pipes" post, is that it is currently -1 out. The past few days have been extremely cold.(ie. highs under 5 degrees) Our bedroom has a mega radiator so is really warm.