Forgive me for posting this and moderators please move or delete if it is offensive or out of lone, but I respect the collective knowledge of this forum and hope someone may know the answer. I have an 04 3.5 Altima. This morning it was 18 degrees, colder than normal for the Atlanta area. The car was left out overnite and when I backed out of the driveway and hit the brakes to stop, there was no stopping. The pedal was hard and fortunately I was going slow so didn't roll to far and no one was on the road. I pulled forward and still no brakes for around 45 seconds when it finally loosened up and I had brakes again.

I have never experienced this in any car. So I am wondering is it water in the fluid that froze and formed a plug or something else? I am thinking at a minimum I will change the fluid.

Wow. That is scary. I have a 2005 Altima SE-R. I live in Ohio and (unfortunately) it stays out in the weather all winter long and I've never had that problem, but others have... http://www.doityourself.com/forum/passenger-cars-suv-service-repairs-no-trucks/293925-brakes-dont-work-cold-weather.html

Thanks for the link, Sounds like the booster. It happened again when I left work last night and it was only 30 degrees out. I didn't like the instance where someone had it happen when they were driving on the highway. I called the dealer service department and the guy said my pads were probably frozen to the rotor. I would think from your link this should be a tsb due to the severity of the problem. I am going to check the booster hose. A few months ago I did do the seafoam cleaner method of sucking in through the booster vacuum. I wonder if this messed up something.