Worcester Digistat CD?

This might help:
www.worcester-bosch.co.uk/cache/file/135/24-hour-digistat-instructions.pdf -

D. Read
December 2008

Sounds like you need to 'recommision' it. It's in the little manual that comes with the transmitter. From memory I think you open both drawers on the digistat and let the display fade away then hold it in line of sight of the boiler before you close the drawers. I've done it quite a few times and it seems to re-establish the communications.

Ian
April 2008