The Mégane II Owners' Club

Hi, on my way to work the 'Boot Open' warning came on unexpectedly and the interior lights came on. I checked when I stopped but the boot was closed. It was a wet day. I couldn't lock the car so I left it and went into work and it was ok when I came back. I'm guessing its a sensor but has anyone had this problem before and should I be worried or should I just put it down to one of those 'Renault electrics' thing? Many thanks.