Tom, this could be several things. Initially, it sounds like you may have a couple roof leaks, or a roof leak and a caulking job around a window. These are probably the cause, and the first items to check, but, depending on the age of the house and what the exterior finish is, it's possible that your walls could be "sweating" and condesation is building up in the stud spaces.
Have your roof checked for leaks or damage, and inspect the caulking around windows and siding. If you don't find problems there, I'd look closely for signs of water at other exterior walls, even pulling carpet away from the wall in a few small places around the home if need be.
Many questions come to mind which could more closely point towards the problem; is your drywall foil backed? What is your exterior finish? What is the age of the home? What type of roofing?
I don't wish to sound alarmist, but it is just possible, as you said, that this could be a problem throughout the house. Post back, if you would, and give some further detail of your home's construction...and keep an eye out for more water.