I got a Archers Choice Rangefinder that I bought new probably 3 or 4 years ago. Its worked great and I really like it. Here recently it seems to work only when it wants to. For example it wouldn't read my block target the other day but it would give a reading for a tractor that was close to it. It has a Lithium battery in it that was replaced last year I believe, so I don't think that's the problem.
one thing i've noticed is that if you block is black, it either has a hard time reading it, or doesn't at all. it does better on lighter colored items.
Try cleaning off the lenses with a lens pen like you'd use on binos or a camera lens. http://www.amazon.com/Nikon-7072-Lens-Cleaning-System/dp/B00006JN3G If you've had it that long and not cleaned it that could be your problem.
