sounds like the cold supply or hot outlet is frozen. if the pipes seem warm then it's probably when the pipes pass under the floor. it's a case of wait for the thaw or get a plumber out to clear the ice and insulate the pipes to try and prevent in future. you will get some heat tracking down the pipes which will make them warm, but not enough to defrost. main cold supply to cold taps is probably ok due to it being in larger bore pipe and at higher pressure.
Ian
January 2010