Alright, this is like the second post where no one asked the "really" important question!!

WHAT KIND OF HUMIDITY MEASUREMENT ARE YOU USING? I only trust digital hygrometers. You see, what you are saying doesn't make sense to me all unless, I go WAY back in memory where something similar happened to me. Only I was trying to use an analog hygrometer. I learned rather quickly that "analog" means "doesn't work".

If you ARE using a digital hygrometer, I recommend you calibrate it again and then try again. If you:

A.) are not using a digital hygrometer and
B.) have not calibrated it, then

We can't really help you much.