Hi
I have the same problem with mine, apparantly from what I have read on a few websites it's a common problem with this phone. I have completely switched my base station and the one problem handset off and am only using one handset at the moment. I have just found this following advice which may help:
www.homephonesonline.co.uk/news/details.asp?item=32
Also, saw the manual on this site:
www.bt.com/userguides/downloads/Synergy2150.pdf
I have looked through my manual though and it didn't say anything about this common 'searching' problem! I'm going to try to reset mine, if not it will be visiting my wheelie bin!!!
I hope I have helped.
Paula
Paula Tippins, February 2007