Panasonic camera/camcorder touch screen broken

[MaybeNotThen]

I've got a HM-TA20 camera and camcorder, it's apparently waterproof and shockproof, but somehow the touchscreen has stopped working for no reason at all. No one remembers dropping it, and there's no cracks or leaking or anything like to show why it's broken. It just doesn't respond to anything we do!

Has anyone got any ideas? I've been Googling but with no luck. I'll try the Panasonic support people but they only have online chat for US customers.