Well, I couldn't be bothered to look for my Orange box that had the warranty paperwork in. So ... I cracked it open. Turns out there is a small resister that lurks (actually there are four) on the USB connection. Appears two current limit on the charging side; and that's were I found a problem - one was toast! A quick test of its companion, I was rather amused to find we have similar ones at work :) Even better, I managed to wedge a replacement in - I'm starting to be glad that I've got the 738 unit now!! Anyway, mobiles back. I hope.