I recently took down the vents in our home for replacement, and have yet to put the new ones in place (I'd like to get the walls painted before I do it) but I've noticed that my home is cooling very unevenly. Our bedrooms, office and bathroom are cool, but our kitchen and living room seem to be roasting.
Can the vents on an forced air system cause this much havoc with the air flow?
From what you said it sounds like your ducting is in the attic, you might check to make sure it is all connected sometimes over the years joints fail. You can close the vents in the colder rooms to help in the warmer rooms.