[squeeforever]

I think the flaps Brian was referring to aren't the ones on the vent, but in the duct itself (there just a built in flow limiter). You just close off the lever on the colder rooms and open it up on the hotter ones. My house is the same way, and even with all of them closed for the most part except mine, my room is still quite a bit warmer than the others since mine is the farthest from the A/C unit. Get up in the attic and see if theres any levers on the ducts right before the vent.