Product review (4 stars): It's replacement going strong to date August 2013
Extech 445814 HygroThermometer
BEWARE!! I've owned this instrument since April 2009. A few weeks ago [11/2009] I noticed the room temperature is now PERMANENTLY 176 degrees Farenheit-- just as this reviewer experienced.  The "humidity calibration adjust" screw has no effect on this temperature reading no matter how many times one turns the screw.  Naturally, the "relative humidity" is radically incorrect since it is linked to this unmoveable 176 F temperature.
I have tried reset.  I have tried removing batteries and reinserting new ones. Still 176F.
As far as I can see there is NO WARRANTEE indicated either on the "User Guide" or the packaging.