They had Mcafee internet security but that ran out over the weekend. The problem was there when they still had it though. I have installed AVG and Zone alarm for now. They also have CC Cleaner and Ad Aware. I've just downloaded A2 square free version to install later today. I don't understand why its just the Ebay home page this message appears.
Well I just got back and the error appears to be happening even when the PC is not connected to the internet. I think it's been coincidence that the Ebay page happens to be displayed when the error occurs.
I have just used A2 Square, CC Cleaner, AVG, Ad Aware and Registry Mechanic all of which found nothing.
I'm pretty sure now it's nothing to be too worried about but I', still puzzled why it's (apparently) suddenly started happening.