On Thu, 26 Jan 2012 16:02:40 -0500, "Robert Green"
wrote:

My neighbor asked me to look at her wireless doorbell, which suddenly
stopped working properly. The buttons still work if you move them close to
the unit but they no longer work mounted on the outside of the door frame.
We've replaced the 3 "D" cells in the base unit and the 12V cells in the two
buttons but still no joy.

Any ideas?

How about replacing the button cell battery in the button unit(s).
When the voltage drops so does the signal strength and thus the range.