Just wanted to say that I haven't totally cured the problem yet but that's because I haven't had any time to look at it today. Jet Central have been in email contact and offered lots of support and solutions. I still suspect the problem may be a battery problem but I need some time to get back to the field and do more testing - I remember the good old days of having a back garden in the UK to do that, now I live in a shoe box in Manhatten with no outside to test in!